Plot: They Hunger is a single player horror mod for Half-Life developed by Black Widow Games. It is divided into three chapters, which were distributed on the internet over a span of three years. Current distributions of the game include all three chapters.
Plot: Counter-Strike: Condition Zero is a first-person shooter video game developed by Ritual Entertainment, Turtle Rock Studios, and Valve, and published by Sierra Entertainment and Valve. The follow-up to Counter-Strike, it was released in March 2004 for Windows. Wikipedia