The powerfully named Hercules Napoleon Cameron is, in reality, a whimpering coward. His rival for the hand of Alice Winthrop (Doris Kenyon) is the courageous and dashing Harry Gaines (Louis Calhern). The three of them visit a divey waterfront saloon and find themselves shanghaied. Cameron and Gaines are forced into the service of the brutal Captain Finn (Louis Wolheim), who gives Alice the choice of either becoming his mistress or sharing a cage with a monster that is half-man, half-beast. Before Alice can decide which is the lesser evil, the monster escapes. Cameron finds Alice in her cabin, and when they go up to the deck, they find that the monster has killed the whole crew. Captain Finn tries once more to attack Alice, but he becomes the monster's next victim. Cameron and Alice dive overboard and swim towards shore, followed by the monster. When he finally realizes the threat to his sweetheart, Cameron finds some latent bravery and battles the beast in the water. An abalone snaps its shell down on the monster, and Cameron and Alice land safely on shore.