On a boat moored in the harbor, deep-sea diver Mike Clancy, John Carradine, wakes from a drunken sleep to find his diving partner Jack Burke, Frank Fenton, tied to the bunk bed. Burke hotly demands cash before untying him; Clancy swears the money is in his pocket, so Burke reaches in, grabs the cash, and leaves without releasing him.
Burke heads to Marge's place, overseen by Marge, Gale Sondergaard, the proprietress of the Isle of Forgotten Sins, where hostesses Olga, Betty Amann ; Bobbie, Patti McCarty ; Mimi, and Christine, Tala Birell, work for their keep. Marge is secretly in love with Clancy, and when he finally arrives, a heated confrontation erupts as he beats Burke unconscious in a brutal fistfight. Clancy then reveals a troubling coincidence: he has recognized two men in the room—Capt. Krogan, Sidney Toler, and Johnny Pacific, Rick Vallin—the captain and purser of the Tropic Star, a ship that disappeared six months earlier in the Coral Sea with three million dollars in gold. The implication is clear: the loot may still be hidden somewhere, and the players are drawn into a dangerous chase.
After a scream from upstairs, a shot rings out, and a customer falls dead as Olga sprints away with a gun in hand. In a panic to vanish before the police arrive, Krogan, Johnny, and the diners flee the scene, while Marge and her girls hurry to Burke’s boat. Clancy outlines a plan to the women, and they set off for Marana Island, where Krogan and Johnny run a plantation. Krogan, watching from a distance through binoculars, had predicted Burke and Clancy would try to recover the gold—and indeed they do, joining forces with the women to seek asylum at Krogan’s house for a few days.
The next morning, Clancy and Burke descend in diving suits, while Krogan and Johnny secretly observe from shore as a trunk of bullion is hoisted from the depths. Burke argues for a 60 percent share, claiming credit for providing the boat and crew, and Clancy protests. A tense struggle erupts as Krogan, Johnny, and their men board the boat. Krogan pulls a gun and orders Clancy and Burke into the back room; Johnny nails the door shut. As they cast off, Krogan and Johnny light a fuse attached to explosives on Burke’s boat. Clancy and Burke narrowly escape the blast.
A raging storm drives Krogan, Johnny, and their five island natives back to shore. Marge asks what happened to Clancy; Krogan claims he died, and the tension between Krogan and Johnny escalates as Krogan accuses Johnny of double-crossing him. Johnny draws his gun and they shoot each other, dying in a fatal duel. Clancy returns with Burke, relieved that they will still share the loot, but the weather worsens. The thatched house is battered by wind and washed away by the rising waves.
In the final scene at The Bird Cage Cafe, Marge sits at the cash register with a framed photograph of Diane and Burke propped beside it. Clancy, now wearing a captain’s cap and jacket, sits beside her and quips, “I’ll have to put the bite on you for about fifty dollars,” hinting at future schemes. “You haven’t forgotten about that bungalow on the Riviera, have you?” he adds, and she hands him money while ringing up a clearly labeled “NO SALE.”
