Half-Life 2: Episode One

Taking place in City 17, just after the events of the last game, Half-Life 2: Episode one again follows scientist Gordon Freeman and his friend Alyx Vance as they stabilize a damaged Citadel core to buy time before it explodes, which will destroy the city and the surrounding area. They then rush to make it out of a war-torn City 17 as quickly as possible and also help evacuate any remaining citizens left.