Caught in the Fog.

Wealthy Bob visits his mother's Florida houseboat in order to remove her jewelry and stumbles upon a bobbed-hair bandit and her male accomplice, who mistake him for another burglar. A fight is broken up by the arrival of an elderly couple (still more burglars) who are posing as guests. Bob keeps his identity secret and passes himself off as the butler; the girl and her partner pretend to be the maid and the cook. A couple of idiotic detectives, arrive on the scene, closely followed by a heavy fog that traps them all on board.