A giant six armed octopus, incited by a test of a hydrogen bomb, becomes tremendously radioactive, rendering most defenses useless against it. The octopus drags a fishing trawler under the sea and stops a submarine dead in its tracks. Scientists John Carter (Donald Curtis) and Leslie Joyce (Faith Dermergue) along with a submarine commander (Kenneth Tobey) have the job of stopping the creature before it begins an assault on west coast cities. The creature does reaches the Golden Gate Bridge and the Ferry Buildings and starts to destroy everything in its path. Will the team be able to come up with a formula to defeat the creature?