A group of scientists and their support crew of five sailors land on a remote island in the Pacific Ocean. They are searching for a previous expedition that disappeared without a trace, and to continue their research on the effects of radiation from Operation Crossroads on the island's plant and sea life. The scientists on the expedition are led by Dr. Karl Weigand (Leslie Bradley), and also include geologist James Carson (Richard H. Cutting) and biologists Jules Deveroux (Mel Welles), Martha Hunter (Duncan) and Dale Drewer (Garland). Their party also includes technician and handyman Hank Chapman (Johnson).