Cold Zero: No Mercy is a third-person action-adventure game developed by Drago Entertainment and released for PC in 2003. Players take the role of John McAffrey, a former SWAT officer turned private detective, completing missions that can be approached through stealth or direct combat. The game features a wide range of weapons, including melee options, and allows players to collect items from defeated enemies to sell for cash.

Take the role of private detective John McAffrey and step into a world of trouble in Cold Zero. A deal-gone-wrong has the hero indebted to the mob. He is asked to put his skills of stealth and tactics to use for his underworld overseers. His first mission has him sneaking inside a bioresearch facility and stealing a virus known as "Cold Zero." But what exactly is this virus? Is delivering it to the mob the smart thing to do? Players must find out for themselves as they play through this dark adventure.