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This subject is from the Black Mesa Incident era.
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Opposing Force cover

Opposing Force cover.

"Government cover-ups were not in my job description!"
HECU Marine[src]

This article describes the Half-Life: Opposing Force storyline, chapter by chapter.

The story of Opposing Force interweaves with the events of Half-Life, so that the player catches a glimpse of Gordon Freeman, the main character from the original game. Shephard sees an officer making a pivotal radio broadcast that Freeman overhears in the first game, and visits some recognizable locations.

In the original Half-Life, a Resonance Cascade opens an extra-dimensional rift, which causes Xen aliens to teleport into the Black Mesa Research Facility. The surviving scientists and security guards at the facility struggle to escape. Responding swiftly, the United States military initiates a massive "clean-up" operation to eradicate the alien presence at Black Mesa as well as "silence" any witnesses.

Boot Camp (optional)[]

The training chapter of Opposing Force. Adrian Shephard is bumped to the top of the Advanced Training list. Shephard and his comrades are trained by Dwight T. Barnes, Marine Drill Instructor, in Santego Military Base, Arizona. He works his way through the training exercises overlooked by Drill Instructor Sharpe until he is ready for the field.

Chapter 1: Incoming[]

Opposing Force intro

Goose 3 under attack by an Alien Aircraft.

As the game begins, Shephard is part of the clean-up operation. After his transport aircraft is taken down by an Alien Aircraft and he is cut off from the rest of his unit, the "clean-up" mission is abandoned and Shephard joins forces with the scattered survivors seeking escape.

Before the first chapter of Half-Life: Opposing Force, a short introduction is shown. As Adrian Shephard and his fellow HECU comrades are approaching the LZ (Landing Zone 117) at the Black Mesa Research Facility, his plane (codenamed Goose 7) is shot down by Alien Aircrafts, along with several other V-22 Ospreys (the first one is codenamed Goose 3). The rest of the opening sequence consists of Shephard continually losing and regaining consciousness, seeing a conflict between the Xen aliens and the Marines who survived the crash.

Chapter 2: Welcome to Black Mesa[]


Scientists are carrying a wounded HECU soldier.

After the crash of his V-22 Osprey, Adrian Shephard regains consciousness completely in an infirmary, not too far off from the crash site. He leaves the infirmary, learning that the other Marines who had survived the crash had been killed by the aliens. He makes his way towards the extraction point, where he is told via radio that the military forces are pulling out of the facility.


  • It is possible to load a safe and find the deceased soldier sitting on a non existent chair, clipping through the scientist found in the infirmary that greets Adrian.

Chapter 3: "We Are Pulling Out"[]

We Are Pulling Out3

The HECU evacuate.

As the battle begins to turn into the Xen aliens' favor, Shephard and the remaining HECU troops begin to evacuate Black Mesa.

Adrian Shephard attempts to reach the HECU's extraction point to escape Black Mesa. He has first eye contact with the mysterious Race X that seems to be collecting humans for study in their world. Shephard reaches the extraction point but is deliberately left behind due to the G-Man's actions.

Chapter 4: Missing in Action[]


Xen flora invading Black Mesa.

Adrian Shephard continues his journey through Black Mesa in search of both his comrades and an alternative escape route after being abandoned at the extraction point. After battling Vortigaunts and traveling through a zombie-infested blast furnace, Shephard meets several other Marines from his company who have also been left behind. He joins forces with them as they try to escape from the facility.

Chapter 5: Friendly Fire[]

Massn bomb truck

The Black Ops loading the Xen rock into a truck.

After battling through an office complex filled with Vortigaunts, Adrian Shephard and other HECU soldiers' attempt to find and use an old transit system to escape to the Lambda Core. The Black Ops are first introduced in this chapter as well. Shephard comes across them in a hangar where they are loading a rock from Xen into the back of a truck. Adrian then learns that the Black Ops soldiers have been sent to kill the remaining HECU Marines and cover up the Black Mesa incident. Shephard meets up with several other surviving marines and fights the Black Ops, eventually reaching an underground railway system that leads to the Lambda Complex.

Chapter 6: We Are Not Alone[]

Sprites xen

Adrian's first view of Xen.

Chapter 6 serves as a short interlude in the game with reminders of events from the original Half-Life. Arriving at the Lambda complex, Adrian Shephard sees Gordon Freeman being teleported to Xen. Shephard is also forced to travel through Xen to find a way out of the Lambda complex.

Chapter 6.5 (optional non-canon alternate ending): C4A1TITLE[]

Shephard follows Freeman through the Lambda Complex portal and arrives in Xen; however because the island Gordon landed on has drifted from the portal's exit point, Shephard teleports into empty space and falls through the void, presumably to his death. As he does, his evaluation by the G-Man is terminated, with the postmortem given as "Subject attempted to create a temporal paradox."

Chapter 7: Crush Depth[]

Crush Depth2

Shephard rescues a scientist.

In it, Adrian Shephard finds himself in underwater laboratories where several Ichthyosaurs are being held. After making his way through the labs and freeing a scientist who provides him with information on the area, Shephard is again forced to teleport to Xen and back again to reach a new part of Black Mesa.

Chapter 8: Vicarious Reality[]

Vicarious Reality2

The Barnacle Grapple is explained.

Adrian Shephard is traveling between various biosphere chambers and laboratories featuring massive terrariums used to house Xen fauna being studied by the scientists deep within the Sector E Biodome Complex. Eventually, he reaches an older industrial area and picks up a radio transmission from a group of Marines fighting some kind of massive creature.

Chapter 9: Pit Worm's Nest[]

Pit worm damn it hurts

The Pit Worm is defeated.

Details Adrian Shephard's battle with the monstrous Pit Worm blocking his progress in Waste Processing Area 3. Working his way through the surrounding area (littered with the corpses of the Marines who sent the distress signal in the previous chapter), Shephard manages to dump toxic waste on the Pit Worm, killing it and allowing him to access the next area.

Chapter 10: Foxtrot Uniform[]

Foxtrot Uniform4

Two Shock Troopers and a Voltigore attacking Adrian Shephard and his comrades.

Details the fierce battle raging between the Race X creatures, the Black Ops contingent, including several snipers, and the remnants of the HECU in the last hours of the Black Mesa Incident. Adrian Shephard makes his way through the underground canals and sewers of Black Mesa, fighting through a Voltigore nest, and arrives at the hydroelectric dam featured in the first game. Here, a Gargantua has been trapped on top of the dam and several Marines are attempting to kill it. Shephard uses explosives to destroy the creature and leaves the area through the dam's exposed water pipes.

Chapter 11: "The Package"[]

The Package2

A Black Ops Apache.

This chapter details Adrian Shephard's discovery of the mysterious Black Ops' plan for Black Mesa. He finds them in an underground parking garage, activating a thermonuclear warhead, apparently with the intent of destroying the facility. Shephard kills them and deactivates the nuclear bomb, but later sees the G-Man reactivating it. Adding to the Black Ops, Shephard must face heavy artillery, a black AH-64 Apache, and Shock Troopers.

Chapter 12: Worlds Collide[]

Gene Worm defeated

The Gene Worm is defeated.

After making his way through warehouses filled with Race X creatures and Black Ops fighting, Adrian Shephard arrives at an old industrial area of Black Mesa deep underground where the enormous Gene Worm is attempting to come through a portal from the Race X homeworld. Shephard uses mounted laser weapons to blind and kill it; in its death throes, an enormous teleportation portal spreads outwards and envelops him.


G-Man Xen Op4

The G-Man talking to Shephard in the Osprey.

Shephard regains consciousness inside a V-22 Osprey, confronted by the mysterious G-Man. As the G-Man talks to Shephard a white flash occurs in the distance, indicating that Black Mesa has been destroyed by the nuclear warhead. The G-Man then informs Shephard that he will be detained "in a place where you can do no possible harm, and where no harm can come to you." He explains this is done since Shephard reminds him of himself but is still a dangerous witness. The G-Man walks into a portal, Shephard is detained and the end credits roll.


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