Half-Life
A mysterious alien artifact has been recovered and brought to a top-secret research facility in the Black Mesa facility in New Mexico. When newcomer Dr. Gordon Freeman is assigned to physically test the artifact, things go very wrong when the artifact opens a destructive and unstable portal to Xen. Believing they are under attack from the Combine the enslaved creatures of Xen go on the offensive. Gordon blacks out, and awakes in a now crippled and ruined research facility.
When Freeman, the survivors, and security guards discover the portal has allowed its inhabitants-deadly alien creatures-to enter the facility, they call the government for help. The government, however, already has plans to contain this incident by sending in U.S. Marine black operations units to silencing the witnesses. Gordon travels to Xen and kills the alien enslaving the creatures and frees them from their master.
Impressed by his actions the mysterious figure monitoring Freeman's progress places him in stasis.