"Follow Freeman!"

Walkthrough
Your first concern here is to get through the city and link up with Barney. After taking the supply crates, make sure to tell any rebel hangers-on to stay put and stay in cover: snipers watch over the street outside.

When you go through the door on the left, stay out of sight of the roving blue laser beams. Wait for the sniper to take his shot and then run like hell to the nearest bit of cover. Keep on doing this, leapfrogging from wall to convenient barrel while the sniper reloads (make sure to use the sprint key). Like the last time you faced these guys, a useful tactic is to pick up objects (like the blue bins) with your manipulator and use them as riot shields.

Head along the street as fast as you can until you reach the first truck. From here, sprint round the left to where there's some cover and a suit battery; then get behind the second truck where you'll find some grenades. From behind here, you should be able to see exactly where the sniper is. Aim your crosshairs at the very centre of the window two floors directly above him, then throw. You should land the explosives right in the sniper's perch, blowing him apart. If you carry on to the end of the street you'll find some supplies at the foot of the building the sniper was in.

Facing down towards where you left your squad, the next sniper is in a building at the end of a long road to your left. Head back for the rebels and make them follow you: you'll need them later - but make sure to keep them out of the sniper's way. Just on the right of the next road there's a small blue-lit shop, so get inside, get the supplies and meet the resistance member. Use the same principle to get the next sniper: Use cover to get close (until your're right up against the rubble barricade) then chuck a grenade into his window. Aim for the top of the window directly above him and you'll generally nail him.

Recall your squad and head into the building on your left - but watch out for headcrabs. Proceed cautiously, since a fast zombie will leap up from a hole in the ground at the far end. As you approach you'll hear a resistance guy shouting - follow the sound of his voice and descend into the waterlogged basement. Go into the little boarded-up area on the right, where a citizen lies dying and helpless. Once he's given you his message, zombies will rise all around the basement. Hopefully you've still got your rebels with you, and the zombies shouldn't be too hard to take town.

Once you're sure all is quiet, go for the door... but be very wary of the two fast zombies who'll come rushing forth to greet you. Blast them and continue on your way, right up the staircase to the building's second floor, where you'll need to stay alert for sniping Combine.

Stay exactly where you are, and don't waste too much ammo on the encroaching zombies: soon enough, the Combine sniper will open fire on them, revealing his position to you. Telling your squad to stay put, prime a grenade and edge round the hole in the left wall. It's an easy throw to the sniper's window: toss it in and watch him cook. If you don't have any grenades, or if you run out, there's a whole crate full of them in the centre of the room.

First sniper gone, work your way round the wreckage and Barney will hail you from above. Once he does, get your squad into the staircase leading upwards and tell them to stay where they are. The sniper's won't appear until you pop your head above the upper floor, so do so, but immediately duck back down to the lower floor. Run underneath Barney and get yourself up against the wall, keeping in cover from both the snipers. Edge out to the left and you'll see the second sniper hiding in the left window. Take him out - and remember, SMG grenades are your friends. You'll know you've got him when Barney shouts 'one to go!'

There may only be one sniper left, but go upstairs with utmost caution - there are poison headcrabs loitering about the place. Flatten yourself against the wall on the left - the sniper is just beyond, easy to track by his telltale blue laser sight. Step out quickly and chuck something explosive into his hiding place. If Barney gets up and runs over to you, you'll know all the snipers in the area (and, in fact, in the entire game) are dead.

Follow Barney downstairs and out of the building, onto the street, where he'll open a Combine gate for you. Just through the door to your right, a poison headcrab huddles in the corner, so edge round slowly with the magnum. Another poisonous crab is waiting through the next door, in the corridor to the left - but once it's taken out you can safely run down the passage into the next area.

When you emerge into the little courtyard, don't rush blindly up the steps: there's a turret waiting for you and soon enough Combine soldiers will burst through the door. But there's a pile of explosive barrels nearby that, combined with your gravity gun, will make easy pickings of both these threats. Having done that, climb the stairs, take all the supply crates, and ascend to the top floor of the building.

Up ahead lies the Combine Nexus - in Barney's words, "an old bank or a museum or something." As you keep going along the passage, maybe stopping to admire the Combine troops scurrying like ants in the square below, you'll automatically be spotted by a camera so double-time it down the stairs on the left before the Combine bombard the room. Head right down to the bottom floor and pull up a hopper. Chuck it round the left corner to disable the turret waiting there, then continue, making sure not to step on any mines, out into the street.

Now you must cross the city square under heavy fire from the Combine suppression beam(read big-ass artillery cannon). Really, there's only one way to do this: run like a bastard. A big blue shipping crate to your right houses health packs; just behind it and slightly to the left is the way forward. Keep on going, and if the beam starts to fire, get you and your squad as far away from it as possible before it strikes. Then run really fast again. Round the back of the blue shipping crate, straight on to the other end of the street, and through a small doorway to to the left. There are two Combine soldiers inside; shotgun them and get your people indoors before the artillery strikes again. You're safe in here, so take a moment to catch your breath, heal yourself from the terminal, and ready yourself for the next run.

Open the door. See that bunker straight ahead? You won't be safe in there, so don't bother. Make a run straight on to the other side of the courtyard: it's a long way, but you can make it, killing the trooper in the bunker on the way. Again, stay clear of the beam, and when it fires miles away from you, take the opportunity to run. Ahead, there's a blue door: as you approach it'll open, two Combine soldiers spilling out. Shotgun-rush them and get indoors as quickly as you can. Watch out for another soldier waiting inside for you. Now you're safe again, and leaving via the door on the far right of the room means you'll be too close for the cannon to hit you: take all the time you want in proceeding out into the next part of the courtyard.

Head right, along the front of the nexus building. Two soldiers will run in from the far side - easy to take down with the crossbow or assault rifle. When you go near the steps, however, more soldiers will charge from the building, so it's a good idea to get on top of the concrete hut and position your squad on the little side ramp. When you've dispatched the Elites and soldiers coming down the big staircase, carry on the the far right flank of the building. Here, you'll find a Combine shield wall, easily defeated by pulling out the power cable. Honestly, you'd think that they could do better. Anyway, make use of the terminals and go through the doorway to your left, up the stairs, and into the next zone.

Open the big double doors on the left and you'll be confronted with lasers protecting the next doorway. If you think they might be dangerous, you'd be right: they won't cut you up, but that vent in the floor just to the left of the doorway is in fact a turret. Rearm from the supply room on the right and then approach the lasers: Barney will deliver a short speech and crowch on the floor. Make sure your squad are well out of the way. Keep to the left wall, where Barney is, and the turret won't be able to see you - its vision cone faces across the hallway. When you cross the lasers, it'll come up from under the floor. Gently pop a grenade into its hole, retreat, and wait for the bang.

Once the lasers go down, Barney will hack the door open. In the next room, there's only one way forwards, and it's in the far right corner. Lasers block the way, and a couple of soldiers will attack you from the shielded corridor on the left. Wait for them to come, kill them, then concentrate on taking out the turrets. Get your squad out of the way, trigger the lasers, pop out and chuck hand grenades. Remember that you can roll grenades along the floor with the right mouse button; and remember that SMG ones also work. Luckily you only have to take on one gun at a time: when they're both history, two soldiers will run down the stairs to the left. Kill them, climb the stairs, ignore the lasers and go straight forward to rescue a medic, who'll grab a gun and join your squad.

Keep your rebels out of the way while you take out the two turrets: the easiest way is to trigger the lasers and immediately sprint to one side, past the guns, so you end up out of their line of fire and in the perfect position to roll grenades right into them. With the guns taken out, head into the small, well-furnished room, where the first generator can be found. Recharge from the health and power terminals, then take out your gravity gun and use the primary fire function to blast the glowing ball from its control beam. As soon as you do so, some soldiers and an Elite will come rushing up the stairwell where you came from. Be ready for them.

When the coast is clear, head out of the generator room, turn the corner to the left and then cross the metal bridge. If you can see a concrete wall with a ragged hole in it at the far end of the bridge, you're going the right way.

Head round to the right and enter the large room with holes in the walls - an armoury of some sort. When you try to get out via the other door, you'll get trapped inside, and Combine troops will begin charging along the corridors outside. Take down as many as you can through the gaps in the walls, and soon they'll start cutting through one of the doors with a sinister hissing sound. When this happens, get ready to make use of the hoppers strewn on the table - not as mines but as improvised projectiles for your manipulator. Get your squad in a good position and wait for the inevitable assault. There are supplies on the shelves and crates on the very top - use the grav gun to drag them down. Soon enough, the door will be rent asunder. Use the available cover to stem the tide. When all the Combine are dead, the door behind you will blow up as well, so you've got to be quick to respond.

Once all is quiet, regroup, heal, and head out the door next to the security monitors. But keep your squad inside - there are two sentry guns to take care of first. The best thing to do is trip the lasers and chuck a grenade into one as you scoot for the cover of the door frame. Wait until the guns power down. Repeat until success. Alternatively you could sprint right between them and get easy grenade shots into both, but they're quite far away and you're liable to get hurt doing so, so if you try it, remember to quick save first. Guns taken out, go through the door on the left, just short of the shield wall, and destroy the second generator.

Now you need to head all the way back to the very first generator room, then across the other metal bridge, where the hallway is blocked by security lasers. Instead of triggering the beams, use the gravity gun to pick up the desk on the floor in front of you, hold it out in front of you as a shield while you approach the turret, and plonk it down right in front of the gun so it can't shoot anything. You'll be free to grab the supply crates and continue on your way without even wasting a grenade. Now go right again, then left, into a room criss-crossed with dangerous-looking red lasers.

Barney encourages you, so pull up the hopper and jump very carefully onto the little ledge on your right. Don't touch the lasers (obviously): they activate deadly gun turrets that will drop you in five seconds flat. Crawl forward, onto the ledge ahead, then edge to the left until you can go no further. Jump over all the lasers onto the little block opposite, and then turn right. There'll be several lasers, some diagonal, at floor level - take a flying leap straight forward and over them. Ignore the scripted explosion sounds. On your right there should be a rounded pillar with ledges around its base - hop up onto the highest of these, crawl round the pillar to the left, pull up the hoppers and drop down to the floor. Head right around the large shelving unit things and you'll see you can crawl under the lasers. Head right, and you'll see the prize - a health terminal and some pick-ups.

Actually, you could pull some of the goodies over to you with your gravity gun: put the same trick won't work on the wall mounted health terminal and anyway you have to get through here to continue the game. Duck under the pipe on your right and, very very carefully, jump up onto the ledge. It looks like doing so will trigger the lasers, but you can actually do it without setting them off (it might be advisable to quick-save first, however). Tiptoe right up to the wall and jump onto the big block the pipes sprout from. From here, it's an easy task to nimbly leap right over all the clutter to land right next to the health terminal, the laser deactivation switch, and safety.

Flip the switch and the lasers will cease to trouble you. Call your squad and continue out the door, into the corridor and then right into a small room where the final generator can be found. As soon as you blow it, head right back out into the corridor, go right, and take up a position on the balcony overlooking the lobby - the Combine are about to assault en masse. They'll come from the doors straight ahead of you, so hold your ground and scatter them with grenades, before picking off the survivors with your crossbow and pulse rifle. When the battle ends, go downstairs and towards the tunnel that they came from - but proceed with caution, as the floor of the passage is littered with hoppers. Make sure you recharge at the terminals on the right wall and grab the supply crates on the left. At the end of the corridor, you'll emerge into a control room of sorts, where Barney will leave you and you'll be left to head for the roof.

Follow Barney's advice and climb the stairs, but watch out behind you for a Combine turret. You can either grenade it, or, if you do it just right, jump and grab it with the grav gun, tipping it over and deactivating it. However you take care of it, ascend the stairwell and wait Combine soldiers will rush down in the opposite direction. Shoot them, climb the stairs, and continue right on up to the roof.

When the level loads, you'll hear the ominous whirr of a Combine Gunship. As soon as you step out of the door, Combine will open fire from the roof straight ahead. The troops rushing you from the right, however, are your primary concern, and only when the initial assault has stopped should you start taking pot-shots at the distant enemies with the crossbow. There's also a sniping soldier on a tower in the far distance - give him a taste of his own medicine. Against the fence to the right there's an infinite rocket supply box, and on the left side of the roof there's some crates, so load up and spend as long as you like watching the fight in the square below. You can shoot at the Strider if you like, but it's unlikely you'll manage to kill it.

Anyway, go down the stairs and across the roof. When the dramatic music starts, a gunship will rise up to take you on. The hardest thing here is trying to stop your friends getting killed - run back to the rocket crate, firing missiles at the gunship, and then just keep firing, keep resupplying, until it's down. Don't worry if you lose your squad mates - yes, it's a tragedy, but some more will come along in a minute. Continue across the roof and you'll come to a large black alloy gate: a drop ship will land on the other side, so stay in cover and use the time to make the most of the health and power terminals. When you've run them dry, edge round the crate to your left and take a few shots at the soldiers disembarking from the drop ship (not with your crossbow, though - save that for later) - but make sure you don't get into the line of sight of the drop ship itself, as its mounted machinegun is pretty nasty. Once all the troops are out they'll open the gate and rush you, so be ready with the hoppers and lots of guns. Afterwards, go through the gate and you'll find yourself right next to the Suppression Beam that was giving you so much trouble earlier. Luckily, it's now powered down. Gordon 1, Cannon 0.

At this point, resistance soldiers will come and join you, replacing any you've lost. Approach the sky bridge but don't press the button yet - shoot at the soldiers with your magnum and your pulse rifle, saving the crossbow for Elites, who show up in a minute. When they do, kill them, then press the button to extend the bridge, at which point the Combine will be able to charge you. They keep coming for quite a long time (although not forever): at the point where you run out of ammo with your long range weapons, it's best to advance cautiously along the bridge with the shotgun. Expect heavy resistance on the opposite side; grenades are your friend. When the coast is finally clear, go into the small room, drop off the broken stairs on your right, and into the next area. I hope you're not allergic to giant three legged biomechanical war machines.

It's strider time. Descend the stairway right to the very bottom, where you'll be greeted by a rocket-launcher toting resistance soldier. Then go outside into the square and prepare for quite possibly the biggest fight in the entire game.

As soon as you get outside, head right, towards the stairs of the nexus building. Feel free to fire off your missiles at the Striders as you climb the stairs and keep on strafing right, through the pillars and out the other side. A Strider will fire its main cannon, collapsing the front of the building. Sprint right, and then straight forward, down into the hole in the ground as another Strider lumbers into view dead ahead. Into the sewer tunnel, collect the health packs and out, right under the Strider's feet. If you have any SMG grenades, fire them off at the Strider's underbelly, then double back up the slope to the left, sprinting as fast as you can way from the Strider, turning right into the little bunker where you'll find supplies and plenty of rocket launcher ammo. From the safety of the bunker, keep popping out and firing off laser-guided death at the two Striders - combined with the heavy fire from rebel-controlled buildings, you should be able to take them both out with the ammo in the bunker. If you do run out of rockets, follow the instructions below (only faster).

Once they're dead, or if there's no more rocket ammo, leave the bunker and go forward. A Strider will appear from the left - take it out from where you are if you can. Head onward, past the big wrought-iron fence, and then turn right, running for the cover behind the rubble pile, at the foot of the building, where you'll find an infinite rocket crate. When you get to it, a friendly rebel will drop supplies from above, and another Strider will lope into the square straight ahead of you. WIth the rockets, it'll be an easy to task to take it down - but watch out for its cannon, which is liable to atomise you if you get in its way. Straight ahead of you, a hole in the wall leads to a useful goodie store. When the battle has quietened down a bit you're safe for the time being, and free to proceed along the street, past the hole in the ground, towards the Combine barricade.

A Strider may appear from the far side of the nexus building, but the likelihood is that the rebels will take it out before it's even remotely dangerous to you; of course, feel free to blow it up, making use of the infinite rocket supply. Anyway, head for the Combine barricade, approach the massive wall and you'll see there's a subway-style staircase leading down to the right. Follow it down to a cachet of useful supplies and the next zone.

Go left down the stairs and you'll find yourself in a massive underground roadway. The way forward is to the right, but as you walk, a Strider will appear behind you and start stomping down the tunnel at you. If you're patient, and at least one of your rebels is armed with a rocket launcher, you can hide as the Strider goes past, then simply camp at your end of the road, crouching behind the wrecked car and drawing fire (since the Strider almost always shoots at you rather than your squad), waiting for your friends to blow it up with their rocket launchers. I sincerely advise you take the Strider down to make life easier for yourself, but if you really can't be bothered, do the following. Before the Strider appears, send your squad further along the tunnel then follow them, breaking into a sprint when you hear the Strider and double-timing it into the building to the left. You'll have a harder (but more exciting) time. Either way, be ready for Combine soldiers coming from the door on the far side of the room as soon as you get inside (explosive barrels are fun).

Head through the door and up the tiny staircase, but be careful - there are numerous soldiers milling around up top, so pave your way with a grenade or two. Try to stay away from the windows if you've left the Strider alive (duh). There are supply crates in the little bathroom to the left. The way forward is at the far end of the room, where a doorway leads to a wide ramp - under which some supply crates are nestled. If the strider is dead, continue merrily on your way upwards - when you get to the top floor you'll see a girder has fallen down, acting as a ramp. But if the Strider isn't dead, then run like hell across the open expanse of the upper floor to the tiny staircase on the far side, where you can take cover as the Strider you neglected to take care of blows the roof up, dropping the ramp.

Wait till the Strider's out of view and then run up the ramp to pick your zigzagging way across the roof beams until you reach safety. Make sure your squad is following, of course. Now, if you want, you can use the infinite rocket-crate to destroy the Strider if you haven't already. Hop across the little gap in the floor, collect all the supplies and move along the corridor, left down the hole in the floor, and on into the next area.

Break through the barricade to meet with a friendly resistance soldier and listen to his speech - the final battle is drawing near. Outside, Striders roam across the cityscape, so be as quick as you can when crossing the road and drop down into the parking garage - where Combine troops are waiting, evidently none too pleased to see you. There are supplies in a little room on the left - get your squad in there and out of sight of the Strider fast. Then take on the soldiers, using the wrecked cars for cover. At the far end of the garage, U-turn round to the right, but keep your squad back. Approach the opening to the street, and three Elites will rush down the rubble slope; dash behind the cover of a car and drop them, with the help of your squad.

Now, wait till the Strider is out of view behind the buildings to the far right, and then lead your squad up the ramp and along the street. At this point, it's almost impossible to actually save your squad mates: don't bother to try and mollycoddle them into surviving. Just run, shoot the enemy soldiers, and hope your guys survive, which is unlikely. Go through the tunnel in the middle of the street and turn the corner to your left and you'll see a pile of wreckage straight ahead. As you approach it, a Strider will rise dramatically, scattering cars like they're made of tinfoil. Don't panic! Run right under the legs of the thing, launching SMG grenades at its belly, and dash left into the dark, cool interior of the building's basement. Don't wait for your friends - they're incapable of realising that following you fast is a better strategy than stopping to pepper the striders with machinegun fire.

Now you can catch your breath for a moment, collecting the supply crate, before moving on. But no sooner do you take a few steps forward than the Combine blow the floor apart, dropping you into a pit. You can avoid it by jumping backwards when the shooting starts, but it doesn't really matter. Take out the soldiers with your magnum and pulse rifle. If you're in the pit, you should be able to climb on the cars to escape; otherwise just sidle round the left edge. Head for the big wide ramp leading upwards into daylight, and a couple of rebels will miraculously appear from behind to join you.

The next section is one of the hardest in the game, but luckily more resistance soldiers will keep spawning behind you and running up to join the fight. Step out into sunlight; two soldiers will start shooting from a rooftop. Kill them and climb the ramp.

Soldiers will continuously appear from ledges and windows to snipe at you. Just lay down fire with the magnum, shotgun and pulse rifle as you run through the building, turning left at the top of the ramp, slipping through the wall of wreckage and right again into a small passage and some momentary peace. Striders will shoot at you continuously - be on the lookout for their cannon blasts, as well as tricky combine grenades (it's advisable to get used to using G to quickly pull out the gravity gun - with quick reflexes, you can chuck the grenade away). It's often a good idea to stay in what cover is available and only move when the Strider is out of sight. Use your own grenades to blast dug-in opponents in high windows.

Once you're safe in the first passage, climb the stairway with shotgun at the ready in case any soldiers are waiting at the top, then grab the supply crate. It's tempting to jump over the low concrete wall and collect the three other crates - but be very careful, because soon one of the Striders will target its cannon on the area and blow a gaping hole in whatever's in its way. Lead your troops over along the ledge to your left, through the door and down the rubble slope to ground level, fending off soldiers in the windows and an Elite coming from the right. When the Strider blows up the enclosed room just to the right of you, stay away until the smoke has cleared. Then keep in cover, blasting away at the soldiers until another cannon blast destroys the block at the far end of the room - you'll know when it happens.

Get behind cover until the Strider has passed and then sprint through the new opening, turning left to snipe the far-off soldiers in the upper windows with your crossbow. Drop down to the floor below and lead your men into the tiny room to your left.

Catch your breath, resupply, and then it's upwards and onwards through the jumble of broken concrete, up the ramp and right until you're in cover. Soldiers and an Elite will assault ahead and from the left; more will snipe at you from the rooftop. Move forward along the right wall of the room, behind the bent and broken metal windows, hopping from cover to cover, taking out the troops on the ground first and then the ones in the windows. There are three supply crates just begging to be smashed, and once you've dropped the soldiers, cross to the blue-lit room where you'll find sweet health and power terminals and plenty of supplies.

Climbing the little staircase on the right, you'll find yourself on the rooftop (watch out for any surviving Combine who might still be up here). There's a rocket supply crate, two Striders and a gunship bombing around making life difficult. Keep in cover and keep firing missiles at the Striders and Gunship until they drop, making use of the health terminals on the floor below when you're near death, and the rocket crate when you run out of ammo. Combine troops will also snipe at you from buildings to the left (if you're facing the rocket crate) but they're a secondary concern. Crossbow them if they become a problem.

Remember that even if you suck the health terminals dry, resistance medics on the floor below can patch you up. When both Striders have collapsed under your withering stream of rockets - you'll know because dramatic music will play for a few seconds - get up on the top level and walk across the thin metal beams. Say goodbye to your resistance chums as they can't follow you. First right, then left - it's easy to work out where to go. Soon enough you'll come to a large hole in the wall that opens onto the street. Drop down and meet up with the rebels on the ground.

There isn't much point shooting at the Combine soldiers - and you'll soon see why. Go forwards along the street and you hear an almighty crash. That's right, Dog has finally arrived, with Barney tagging along behind, to open a can of robotic whoop-ass on the Combine. Watch the fireworks, mop up any survivors, and meet with Barney. He'll talk for a bit, then run over to Dog. Follow him and Dog will open a way into the Citadel for you. Say goodbye to Barney, Dog, and the rebels as you drop down into the hole - from this point on, there is no turning back. Along the sewer tunnel lies the citadel, Alyx, Dr Breen and the penultimate level - Our Benefactors. Good luck!