Soldier of Fortune II: Double Helix is a video game created by Raven Software, a sequel to Soldier of Fortune. It was developed using the Quake III: Team Arena engine. Once again, Raven hired John Mullins to act as a consultant on the game. Based on comments and criticisms of the original game, Raven Software developed Soldier of Fortune II to be a more "realistic" game, with tactical shooters like Operation Flashpoint: Cold War Crisis and Tom Clancy's Rainbow Six as inspirations rather than Quake. A sequel titled Soldier of Fortune: Payback, made by Cauldron HQ was released for Microsoft Windows, PlayStation 3 and Xbox 360 in 2007.

The theme of the sequel is germ warfare, as the mercenary Mullins and his new partner Madeline Taylor travel to Colombia to investigate a viral outbreak in a small town, only to link it to a shadowy organization called Prometheus. The virus, called Romulus, is followed by a computer virus called Remus which is programmed to delete files on any computer in the world, in this case, files relating to Prometheus and Romulus, so an anti-virus cannot be formulated. Prometheus then plans to blackmail the G8 countries at a summit in Switzerland for billions of dollars. It is revealed throughout the course of the game that a mole inside The Shop may be feeding information to the terrorists.