Admiral Nelson has been brainwashed. After getting a vital energy source, he attempts to kill Crane and the visiting Dr. Land in an undersea cave. He then returns to the sub, gasses the crew and sets the reactor to blow. Can Crane recover and return to the Seaview before Nelson can destroy it?
Elenco: Richard Basehart , David Hedison , Robert Duvall , Terry Becker , Del Monroe , Paul Trinka , Richard Bull , Robert Dowdell .