You are Gordon Freeman, a young research associate in the Anomalous Materials Laboratory. You have limited security clearance and no real idea of just how dangerous your job has become, until the morning you are sent alone into the Test Chamber to analyze a strange crystalline specimen. A routine analysis, they tell you. Until something goes wrong. In this legendary FPS, players enlist the help of traumatized scientists and trigger-happy security guards to get through high-security zones, sneaking and fighting your way through ruined missile silos and Cold War cafeterias, through darkened airducts and subterranean railways. When you finally come in sight of the surface, you realize that the inhuman monsters aren't your only enemies-for the government has sent in ruthless troops and stealthy assassins. Their orders seem to be that when it comes to the Black Mesa, nothing gets out alive... and especially not you.