The Big Mouth

During his annual two-week fishing holiday, Gerald Clamson reels in Syd Valentine, an injured gangster in a scuba diving suit. Syd reveals he has stolen diamonds and hands Gerald a map showing their location. They barely escape as frogmen from a yacht machine-guns the beach, forcing Gerald to flee for safety.

They swim ashore and locate Syd, but Gerald opts to end Syd's threat by shooting him. The killing silences Syd's claims and pushes Gerald deeper into the diamond search. The beach is left scarred by the earlier firefight.

Thor, the mob leader, fires a torpedo from his yacht to blow ashore, creating a crater and erasing evidence of Syd's murder. The violent display shows the reach of the criminal underworld and the danger Gerald faces. The police ignore Gerald's account of events.

With law enforcement uninterested, Gerald travels to the Hilton Inn in San Diego, following Syd's clue about where the diamonds might be hidden. There he meets Suzie Cartwright, an airline stewardess, and begins a tense search while trying to stay out of sight. He must avoid the hotel staff and keep a low profile as the chase starts.

To stay ahead of the gangsters and hotel detectives, Gerald disguises himself in a look inspired by Professor Julius Kelp from The Nutty Professor. He uses the disguise to move around the hotel while continuing the search for the diamonds. Suzie becomes involved as their relationship deepens under the mounting pressure.

As Gerald passes by, each gangster spots a near-identical lookalike of Syd and suffers a nervous breakdown. One imagines himself as a dog, another as a Larry Fine lookalike, and a third becomes a stutterer. The surreal reactions heighten the comic chaos while the hunt for the diamonds narrows.

The only believer in Gerald's story is a man who identifies himself as an FBI agent, but he is later revealed to be an escapee from an insane asylum. This deception adds another layer of mistrust and danger to Gerald's mission. The encounter leaves Gerald more cautious as he continues his search.

The climax builds as Gerald is chased through Sea World San Diego by Thor's mob, a rival gang that had made a deal with Syd, and a group of Chinese smugglers disguising the diamonds as plastic pearls. He dodges capture by weaving through crowds and rides. The environment becomes a high-stakes chase.

Gerald disguises himself as a Kabuki dancer, but the pursuit continues until Suzie arrives with a helicopter. She rescues him by lowering a rope ladder, allowing him to escape. The dramatic rescue marks a turning point as they head back toward the Pacific.

Back in the Pacific, Syd reappears and is chased by rival gangsters into the water. Gerald and Suzie walk away together, their romance solidified as chaos subsides. The diamonds themselves remain undiscovered.

Despite the frantic search, the diamonds are never located, leaving the central heist unresolved. Gerald reflects on the strange sequence of events as he considers what truly happened.

In the final scene, narrator Bogart faces the camera and solemnly declares that the tale is true, then the camera pulls back as De Vol walks away on the breakwater. De Vol is dressed in a business suit with trousers missing, carrying a briefcase, ending the tale with a quiet, comic twist.