Please note that minor spoilers will follow, though it´s nothing that publisher Konami wasn´t prepared to divulge leading up to the game´s release. Portable Ops takes place around 1970, and the story begins with Snake getting assaulted somewhere in South America. He´s thrown in the slammer, and soon he comes face-to-face with one Lt. Cunningham, an ex-CIA interrogator who appears to have an electric cattle prod for a leg. He´s bad news for sure, but Snake doesn´t give in to Cunningham´s first line of questioning about something called the Philosophers´ Legacy--something that Metal Gear Solid 3 players will know a thing or two about. Cunningham promises he´ll be back, and leaves Snake to rot. But it turns out Snake isn´t all alone. A nearby cell mate is a resourceful young man who helps him break free; he recognizes Snake as the legendary Big Boss, a patriot and a hero. Snake, freed from his prison, is left to wonder what heavily armed members of the FOX Special Forces unit are doing in a Soviet base in Colombia. The answers may shed new light on the Cuban Missile Crisis of the ´60s. Used to working alone, Snake reluctantly agrees to collaborate with his new friend to find some answers. His new friend is Roy Campbell.
source:
http://www.gamespot.com/psp/action/metalgearsolidpo/news.html?sid=6162178&tag=topslot;action;1