A marine biologist and a government agent investigate mysterious deaths and rumors of a sea monster in a secluded ocean cove, and find themselves involved with a marine biology professor conducting secretive experiments, international spies trying to steal his secrets, a radioactive light on the sea bottom, and the malevolent thing which guards it.
| Actor | Role |
|---|---|
 Kent TaylorDr. Ted Stevens, alias Ted Baxter | Dr. Ted Stevens, alias Ted Baxter |
 Cathy DownsLois King | Lois King |
 Michael WhalenProf. King | Prof. King |
| RRodney BellWilliam S. 'Bill' Grant | William S. 'Bill' Grant |
 Phillip PineGeorge Thomas | George Thomas |
| VVivi JanissEthel Hall | Ethel Hall |
 Helene StantonWanda | Wanda |
 Pierce LydenAndy, the Janitor | Andy, the Janitor |
| MMichael GarthSheriff | Sheriff |
| NNorma HansonThe Phantom | The Phantom |