Sons of Liberty is the successor to the 1998 classic, Metal Gear Solid. The game starts off a few years after the Shadow Moses incident that occurred in 2005. Snake and Otacon have formed the Anti Metal Gear group called Philanthropy, and are on the trail of a new metal gear being built by the Marines. Snake infiltrates a tanker that is holding the new experimental weapon, and encounters a lot of old acquaintances including Revolver Ocelot and Liquid Snake. The major turn for the series is that it introduces a new character Raiden, with whom you play through most of the game as infiltrating the Big Shell. Raiden works along with Solid Snake to over come the Patriots and destroy the new experimental weapon called Arsenal Gear that the facility is housing.