Mark IV Thermonuclear Device

"The biggest embarrassment has been Black Mesa facility, but I think that's finally taken care of itself... quite so."

- The G-Man

The Mark IV Thermonuclear Device, nicknamed "The Package", is a thermonuclear warhead stolen by the Black Ops, used to destroy the Black Mesa Research Facility.

Overview
The bomb is first introduced in Opposing Force's sixth chapter, Friendly Fire, where it can be seen in the back of a truck, guarded by two Black Ops assassins, and near the rocket from which it was removed, in an Ordinance Storage Facility connected to Sector E Materials Transport.

Later in the game, in the thirteenth chapter, "The Package", Shephard discovers two other Black Ops assassins setting up the bomb in an underground parking lot under the large Ordinance Storage Facility and connected to Sector E Materials Transport. After killing the assassins, he deactivates it. Afterwards, he proceeds to a nearby room with a view on the truck, and witnesses the G-Man reactivating it. He cannot go back at the truck, making the destruction of Black Mesa inevitable.

The bomb explodes when Shephard is detained by the G-Man aboard an Osprey at the end of the game, when a white flash covers the screen while the G-Man makes a slight pause in his monologue.

Instructions
The following instructions are written inside the bomb's cap:

Behind the scenes
Although subsequent games tend to somehow disregard the Gearbox expansions' storyline, series' writer Marc Laidlaw has confirmed that the destruction of the Black Mesa Research Facility at the end of Opposing Force is canon.

Trivia

 * In the chapter Friendly Fire, the bomb only appears as a rough brush, while it is a detailed model in the chapter "The Package".

List of appearances

 * Half-Life: Opposing Force