Barney Calhoun, an undecided major after two years at Martinson College, is employed as a mid-level security officer at the Black Mesa Research Facility, with Level 3 security clearance and is accommodated in the Area 8 Topside Dormitories. He is friends with Gordon Freeman and Isaac Kleiner, who are also employees of Black Mesa.

Dr. Gordon Freeman is the protagonist of the Half-Life series. Freeman is a theoretical physicist, forced to defend himself and the human race in a conflict against hostile aliens and other enemies after a failed experiment causes a worldwide alien invasion. He doesn't speak, communicating through sign language, gestures, and facial expressions. Awkward, probably nerdy.

Dr. Isaac Kleiner is a scientist, and a prolific author of several works on teleportation and interdimensional travel, and one of the few survivors of the incident that took place in the Black Mesa Research Facility. such as "Oh, fiddlesticks" or "Oh, fie!". He acts politely and amicably towards his allies, from those he share a friendly relationship. Isaac also maintains an optimistic outlook on things; he generally considers the best outcome even under dire circumstances.

As seen on his sweater after hours, Eli is presumably a graduate of Harvard University. Vance is employed at the Black Mesa Research Facility, working in Sector C's Anomalous Materials. As a full-time employee of Black Mesa, he lives in the facility itself with his wife Azian and their young daughter Alyx. Eli is warm, good-humored, and charismatic, holding everyone around him in the aura of his personal charm. He's black. He wears the standard scientist uniform, complete with the itchy tie. He would be that kind of person to call everyone he knows by nicknames, like Kleiner, who he calls "Izzy" based on his first name, Issac.