Half-Life 2: Episode One

Half-Life 2: Episode One is the first of a planned trilogy of stand-alone expansion episodes for the 2004 first-person shooter Half-Life 2. Set immediately after Half-Life 2, it takes place in the war-torn City 17, where the player must face the consequences of their actions from the main game. While it continues the story of Half-Life 2, it does not require the original game to be installed or registered to a Steam account. Episode One uses major Source engine upgrades introduced since Half-Life 2, especially high dynamic range rendering and an improved facial animation system. Episode One launched alongside Half-Life Deathmatch: Source, a port of the original Half-Life’s multiplayer that also serves as Episode One’s multiplayer component. Retail copies of Episode One also include Half-Life 2 Deathmatch for players who do not already own it.

Set in City 17 just after the previous game, Half-Life 2: Episode One follows scientist Gordon Freeman and Alyx Vance as they race to prevent catastrophe. With the Citadel critically damaged, they work to stabilize the unstable Citadel core to buy time before it detonates—an explosion that would wipe out the city and the surrounding area. Once they’ve delayed the blast, Gordon and Alyx fight their way through a war-torn City 17, trying to escape as quickly as possible while also helping evacuate any citizens who remain.