A down-on-his-luck entrepreneur (Dick Foran) and his sidekick (Fuzzy Knight) team up with a peg-legged Captain (Leo Carrillo) to take a group of unwitting strangers on a treasure hunt in a remote island castle. The Captain has half of a map to the coveted goods but a mysterious phantom lurks in every shadow waiting for his moment to seize it. One by one, the participants fall victim in the mysterious mansion's dark rooms and secret passageways. It is up to the remaining survivors to uncover the killer amongst them before the trip to the island becomes their last.