The Half-Life series begins in the 2000s, at the fictional Black Mesa Research Facility in New Mexico. Gordon Freeman, a recently employed theoretical physicist, is involved in an experiment analyzing an unknown crystalline artifact; however, when the anti-mass spectrometer beam contacts the crystal, it creates a resonance cascade that opens a dimensional rift between Black Mesa and another world called Xen, causing monsters to swarm Black Mesa and kill many of the facility's personnel. Attempts by the Black Mesa personnel to close the rift are unsuccessful, leading to a Marine Recon unit being sent in to silence the facility, including any survivors from the science team. Freeman fights through the facility to meet with several other scientists, who decide to travel to the alien dimension to stop the aliens. On Xen, Freeman eliminates the alien "leader" and is confronted by the G-Man, who offers Freeman employment before putting him into stasis.[2] Back in Black Mesa, a second alien ... Written by wikipedia.