The game's events take place immediately after those in Half-Life 2, in and around war-torn City 17. Episode One follows scientist Gordon Freeman and his companion Alyx Vance as they fight in humanity's continuing struggle against the transhuman race known as the Combine. When the story begins, Gordon wakes up outside the enemy's base of operations, the Citadel, after being left unconscious from the concluding events of Half-Life 2.