After Black Mesa plummeted into the ground 200 years after the incident, it was brought back to life by a group of Blue-Headed men all named "Jamie". Jamie and all his friends now work at the lab, and ironically enough the same exact thing that happened 200 years ago happens again. Even with Gordon Freeman brought back from the dead.
This is the high point of 2013 folks, this is the full release of Jamie's Mod.
We've significantly cut levels from the game, making the overall "game" a lot shorter than HL1, for the better. Please report any bugs or glitches to us, and we'll fix them in an inevitable 1.1 update. Cheers!