It stars Dick Foran, Peggy Moran, Leo Carrillo, Eddie Parker, Dale Van Sickle, John Eldredge, Lewis Howard, Hobart Cavanaugh, Iris Adrian and Fuzzy Knight.

It is a deserted useless rock to Bill, but by pure chance he stumbles across a treasure map pointing to his island.

The map is presented to him by a peg-legged old sailor, Tobias Clump, after Bill and his friend "Stuff" Oliver saves the man from drowning.

Clump tells them that the map shows the way to infamous buccaneer Sir Henry Morgan's twenty million dollar treasure.

When the ship is ready to leave on the cruise, Bill, Stuff, Wendy and Thurman are accompanied by cousin George, Jasper, a small-time gangster by the name of Rod Grady, his wife Arleen and a private investigator, McGoon, who has tried to find evidence that the cruise is a fake and uses false advertising.

The ship sails and is soon lost at sea, until Bill discovers that a magnet has been placed on the compass to deliberately put them off track.

Bill mistakes the accidents for Stuff's planned surprises, part of the "haunting" experience included in the treasure hunt.

The phantom that stole part of the treasure map from Clump reappears and warns Wendy and tells her that she will die if she stays on.

A man in a cape kills Rod in front of Arleen, but when she gets back to the rest of the group the private investigator McGoon suspects her of being the killer.

Bill, Stuff and Wendy escape, but only to find themselves trapped in a secret passage inside the castle walls.

The rest of the group enter the treasure chamber and opens the chest, only to find the skeleton of Sir Henry Morgan himself.

Disappointed the group members make their way back to the surface, where they meet a government agent, who offers to buy the whole island from Bill in order to build a naval base.

[3] Archer Winsten of The New York Post declared the film "a nicely paced quickie" whose problem was "that it tries so hard to be scary, funny, and mysterious that the component parts never come together".

[6] From retrospective reviews, Hal Erickson of AllMovie commented that Horror Island "remains an enjoyable outing from fade-in to fade-out", noting that "the identity of the "mystery" killer is fairly obvious from the outset, though the screenplay cheats a bit by rendering the villain helpless during one of the murders".