On the night before he is to leave on a four-week fishing trip, Larry Lawrence, New York's "Walter Winchell" of crime, receives an order from gangster Frenchy Duval to visit him at his hotel.  In the hotel hallway, Larry becomes involved in a shooting and, believing that he has killed Ramon Mederos, hides in the steamer trunk owned by guest Mary Carter, who is leaving that night to take possession of an inherited haunted castle on a small island off the coast of Cuba.

Upon emerging from the trunk, Larry finds himself aboard a steamer accompanied by his valet, Alex.  When Mary receives a death threat, Larry comes to her aid as a "ghost breaker."  Despite warnings from Geoff Montgomery, an old acquaintance, and Parada, her Cuban advisor, Mary and Larry remain undaunted in their determination to visit the castle.

The night that the steamer docks, they make their way to the island, where they encounter a ghost, a zombie and disembodied voices before coming upon the dying Parada, who tells of his stabbing and a fortune hidden beneath the castle.  In the castle basement, they discover a silver mine and Parada's murderer, Montgomery.  After Alex dispatches Montgomery, daylight dawns, and they all leave the island in much brighter spirits.