 The ballistic missile submarine USS Montana sinks under mysterious circumstances. The doomed boat settles on a ledge several hundred feet deep and on the edge of an even deeper ocean abyss. US Navy SEALS are brought in to salvage the sub s missiles and an experimental civilian deep water oil-drilling rig is commandeered to help. All goes well until the SEAL leader suffers from high pressure madness and the rig is visited by the "Non-Terrestrial Intelligence" that apparently lives in the abyss. The ensuing struggle results in a race against time to prevent World War III and a reunion between the estranged couple that designed and operate the oil rig.