Contagion is the launch title for Monochrome LLC who's Founder is responsible for the award-winning and #1 played Half-Life 2 Modification, Zombie Panic: Source. Eugene, Marcus, and other Survivors return in the spiritual successor of the popular Half-Life 2 Modification Zombie Panic: Source! Contagion is a cooperative survival horror FPS built on the latest Source Engine where players are forced to watch their ammo and aim carefully otherwise be overrun by the zombie hordes. Source: The Game Website.