Mr. Moto in Danger Island is a 1939 American mystery film directed by Herbert I. Leeds and starring Peter Lorre, Jean Hersholt and Amanda Duff.

On the ship taking him to San Juan, he unwillingly acquires the services of a dim-witted, but good-hearted professional wrestler Twister McGurk after he teaches him jujutsu.

The ambulance that is to take him to the hospital is hijacked by the smugglers led by Captain Dahlen who plan to execute him, but McGurk arrives in time to save him.

As only a few people around John Bentley, the governor of Puerto Rico, knew that he had reported that he needed an appendicitis operation, he deduces that one of them must the leader of the smuggling ring.

Despite being old friends, there is much tension between Bentley and Colonel Castle over the latter's inability to solve the Graham murder case or to discover who the diamond smugglers are.

After hiding from the police, Mr. Moto tells McGurk that he sent the cable himself in order to infiltrate the smuggling gang who have kidnapped Joan Castle.

Moto has Dahlan taken to the hospital and announces that based on what the doctors have told him, Dahlen will reveal who his boss is at 8 pm.

Moto reveals that Colonel Castle has been framed and the leader of the gang is Mr. Sutter who is caught throwing the knife into Dahlen.

With Sutter arrested, Joan declares her love for George Bentley, the governor's son, while McGurk thanks Moto for teaching him jujutsu.