Phantom

A Soviet nuclear submarine captain is ordered to take a small group of KGB officers on a voyage so they can perform a test of some new technology, highly classified. As the voyage progresses he learns there is more to their mission, the KGB officers are rouge, and the fate of the world hangs in the balance.
Ed Harris delivers an excellent performance as the captain. David Duchovny plays a KGB officer in charge of the mission. The story was inspired by a real world event, the details of which remain classified.