Captain Thorne Sherman (James Best) and first mate Rook Griswold ("Judge" Henry Dupree) deliver supplies by boat to a group on a remote island. The group, consisting of scientist Marlowe Cragis (Baruch Lumet), his research assistant Radford Baines (Gordon McLendon), the scientist's daughter Ann (Ingrid Goude), her former fiancée Jerry Farrel (Ken Curtis), and a servant Mario (Alfred DeSoto), welcome the captain and his first mate. Before the two visitors can get too comfortable though the islanders...