"Given the rapid changes in PC gaming, we expect episodic games will have the same impact on single-player gaming that Counter-Strike had on multiplayer," said Gabe Newell, president and co-founder of Valve. "The frequent releases of upgraded technology and new content works better for both consumers and developers, and is one of the key reasons Counter-Strike grew to be 80% of the online action market. We decided that a follow-up to Half-Life 2 delivered in 18 months with our first episode was more in tune with what our customers want than waiting 6 years for another monolithic product."

Episode One offers a new single player experience created by Valve, and is designed to be four to six hours in length. Stepping into the hazard suit of Dr. Gordon Freeman, you face the immediate repercussions of your actions in City 17 and the Citadel. Alyx Vance and her robot, Dog, will accompany you in your efforts to aid in the human resistance's desperate battle against the totalitarian alien menace of the Combine.