The story concerns the nautical exploits of the titular captain and his rambunctious crew aboard their ship The Black Tiger. After some episodic adventures they capture a small humanoid, referred to only as the Yellow Creature, with whom Slaughterboard develops a strange platonic infatuation. His loyal crew gradually fall prey to misadventure and the bookends with the Captain and the Yellow Creature forsaking piracy for fishing on the creature's pink island. The book is notable for Peake's poetic style and his fineillustrations of the many fantastical beasts on the island.