AllMovie

The Seaview is crossing the equator, its crew enjoying a light moment or two without a major mission at hand, when a war alert comes through. The sub's failsafe device is unlocked and Nelson (Richard Basehart) and Crane (David Hedison) prepare for a nuclear missile launch, when the ship's missile officer (Donald Harron) suddenly refuses to obey the order. And when the alert proves to be a false alarm, they find themselves unable to disarm the missiles or prevent their detonation.