An engineer, a psychologist and several other disparate types take part in an experiment to see if people can live for extended periods of time in a city built under the ocean.

Don Gregor, the son of famous plastic surgeon Dr. Boris Gregor, begins to hang around with young criminal Vic Brady and carry a gun. The pair attempt an armed holdup, and when things start to go wrong Gregor accidentally kills a night watchman. Fearing that Gregor plans to turn himself in, Brady kills him and blackmails Dr. Gregor into giving him a new face.