Based on a novel by Richard Hughes, this drama takes an unusual look at both seafaring pirates and the true nature of children. The Thorntons, a British family living in Jamaica, decide to pull up stakes and sail back to England after Frederick Thornton (Nigel Davenport) and his wife (Isabel Dean) decide that life in the Caribbean is having a negative effect on her children's sense of order and discipline. While returning home, their ship is attacked by Capt. Chavez (Anthony Quinn), who along with his first mate Zac (James Coburn), begins to loot the ship for valuables. However, in the midst of the confusion of the pirate raid, the Thornton children scurry onto the pirate ship, and it's not until they've left the other ship behind that Chavez and Zac discover that they have new passengers. While most of the pirates are unenthusiastic about having a pack of kids on board, Chavez declares that they must be allowed to stay on board until they can be taken to a safe port. As they get to know each other, Chaven develops a soft spot for the children, especially ten-year-old Emily (Deborah Baxter), but in time, the kids' mischievous playfulness begins to transform itself into something more sinister. The supporting cast includes Dennis Price, Lila Kedrova, and Gert Frobe.