In 1995, the gigantic fortress within Outer Heaven that was founded by a legendary mercenary is constructing a gigantic weapon of mass destruction. In the U.S. Government's support, Special Forces Unit FOXHOUND commander Big Boss sends in his most trusted agent Gray Fox. However, Gray Fox disappears with his last message simply reading "Metal Gear...". Rookie FOXHOUND recruit Solid Snake infiltrates Outer Heaven and put a stop to the world's most powerful weapon.