Tom Clancy's Rainbow Six: Lockdown is a 2005 tactical first-person shooter video game published by Ubisoft for the PlayStation 2, Xbox, GameCube, and Microsoft Windows. It is the fourth game in the Rainbow Six series. The game's plot follows Rainbow, an international counterterrorist organization, as they battle a terrorist organization that has stolen a deadly bioweapon. The PlayStation 2, GameCube and Microsoft Windows versions were developed by Red Storm Entertainment and the Xbox version was developed by Ubisoft Montreal. Lockdown was first released on August 3, 2005 for mobile phones, with console versions being released in September of the same year and the PC version being released in February 2006. The game received average reviews mostly due to its departure from traditional Rainbow Six gameplay. A sequel, Tom Clancy's Rainbow Six: Critical Hour, was released on March 17, 2006.