The player reprises his role of Dr. Gordon Freeman, who must immediately face the repercussions of his actions in City 17 and the Citadel. Freeman reconnects with Alyx Vance and her robot, Dog, as they continue their support of the resistance's battle against the Combine forces.

The intense, real-time gameplay delivered in Half-Life 2: Aftermath is made possible only by Source, Valve's proprietary engine technology which has been enhanced with new rendering technology and advanced artificial intelligence to deliver new levels of graphics and character interaction.