The nuclear submarine Neptune, which accidentally collided with a radar-less freighter, has sunk to a depth of 1450 feet and now sits, helpless with its stern split open, on a ledge above an ocean canyon, ready to slip off at any time. The sub's commanding officer (Charlton Heston) and 41 of its personnel are miraculously still alive but they only have enough oxygen for 48 hours. Gray Lady Down is an exciting suspense-adventure drama detailing the heroic rescue operations conducted by the U.S. Navy's Deep Submergence Rescue Unit to save the stricken sub's crew. The cast includes David Carradine as a maverick Navy Captain who pilots the "Snark" — a tiny underwater rescue craft of his own design.