An underwater race that lives beneath the floor of the Pacific Ocean, has developed a large "missile ejector" and is test firing it on small islands. Stingray is sent to investigate and manages to prevent an attack on the West Coast of the United States. The underwater race devises a trap designed to lure the crew of Stingray to its doom and to launch an attack on Marineville.
Troy Tempest is on standby duty while a ship carrying a radioactive isotope nears its port destination. He is supposed to rest. While he does so, he ponders how he should dress to a costume party hosted by Atlanta Shore. Suddenly, he gets a summons to help the stricken ship. Or does he?
A ship with a load of gold disappears after hitting an iceberg. Meanwhile, the Stingray crew is enjoying a shore leave in Casablanca. While there, Troy Tempest is on a date with Marina while "Phones" is offered the chance to buy a purported treasure map for $500. "Phones" only has $200 but blackmails Troy by reminding him he has a date the next night with Atlanta Shore and gets the remaining money to buy the map. However, the map indicates the treasure is out of the way for Stringray's return course to Marineville. Marina, feeling sorry for "Phones," alters course ...
When a seemingly indestructible craft is sighted heading towards Marineville on a collision course, the eccentric Professor Burgoyne is called in to help develop a new super missile with which to destroy it.
Commander Shore appears to be a traitor after Marineville's security has been breached. This forces Troy Tempest to arrest his commanding officer and causes heartbreak for Atlanta Shore. However, just when the situation seems to be resolved, a complication occurs.