Metal Gear Solid 4: Guns of the Patriots

Five years after Big Shell, Solid Snake — genetically engineered to age at an accelerated rate, and now a frail old man in his forties calling himself Old Snake — is dying. FOXDIE, the virus once used to kill Liquid Snake, has mutated and is now killing him too, degrading his body a little further every day. Roy Campbell and Naomi Hunter recruit him for one last mission: track down Liquid Ocelot, the Patriots-defying warlord who has stitched Liquid Snake's mind into Revolver Ocelot's nanomachine-grafted body, and is threatening to hijack SOP, the AI system that arms and controls nearly every private military company on Earth. Snake's manhunt takes him through a Middle Eastern warzone, a South American guerrilla village, an Eastern European city under PMC occupation, and finally back to the frozen ruins of Shadow Moses — reuniting him with Otacon, Meryl, Raiden, and other old allies along the way, as the truth about the Patriots, the SOP system, and Snake's own origin finally comes to light.