Johnson, an agent for the Liquor Control Department, is dispatched to disband a gang of cut-throat still operators on an island in the Everglades run by Doc. He is discovered by the moonshiners and nearly escapes by diving into the crocodile-infested swamps. Completely exhausted by the long swim. he stumbles and falls and is stabbed by a masked female killer that lurks along the beach every full moon. Finally making his way he stumbles along the Cuckoo Bird Inn run by Mrs. Pratt, a twice-widowed ex-showgirl and owner of the inn. She also has a beautiful daughter named Lisa who is kept chained up in the attic except for at night since she won't escape into the darkness that she fears. Harold, the inn's caretaker, is a taxidermist whose mental and physical deficiencies are advantageous to Mrs. Pratt. While the inn's guests scheme against Johnson, the masked killer has made many unsuccessful attempts on his life. Later he finds Doc's corpse being readied for stuffing and realizes that he must discover the killer's identity or suffer the same fate. In the exciting climax, Johnson wrestles with the knife-wielding killer in the Chapel of the Dead as a fire threatens to reduce the island to cinders.