Half-Life 2: Episode One is the first of a trilogy of expansion packs/episodes for Half-Life 2. The episode takes place immediately after the end of Half-Life 2, in and around the war-torn setting of City 17.
The player is forced to deal with the effects of their actions during the main game. The episode is a stand-alone game; while a continuation of Half-Life 2, it does not require the original game to be installed or registered to a user's Steam account to play. It takes advantage of several major upgrades to the Source Engine since the release of Half-Life 2, primarily its high dynamic range rendering capabilities and the upgraded facial animation system.
