Half-Life 2 Episode One is a first-person shooter game developed and published by Valve. Half-Life 2 Episode One marks the commencement of a series of episodes continuing the narrative from Half-Life 2. Set directly after the events of Half-Life 2, the game unfolds amidst the turmoil of City 17's war-torn landscape. Following scientist Gordon Freeman and his ally Alyx Vance, the story follows their quest to flee City 17 following the triumph over the Combine forces and the intense Citadel battle.

• Half-Life 2 Episode One