In the bustling port of Port Said, the British Navy is preparing for upcoming naval exercises with the French fleet, but these plans are suddenly thrown into jeopardy. The delay occurs because the British Secret Service receives a warning about potential sabotage, signaling that hostile agents may be lurking among the ships and couriers. Among the ships docked in Port Said is Madame Delacour, played by [Virginia Field], the wife of the French naval admiral. She is accompanied by her daughter Marie and is soon surrounded by a mixture of intrigue and danger when various characters start to reveal their true intentions.
Eric Norvel, a charming yet somewhat goofy man, befriends Madame Delacour, as does Rollo Venables, a less serious character portrayed by [Robert Coote]. A mysterious figure also appears who impersonates Mr. Moto, a character played by [Peter Lorre], but this "Mr. Moto" is not quite who he seems. When the ship docks, Norvel’s true nature is exposed: he lures Mr. Moto to his death, revealing his role as an agent working against the secret plans. But it turns out that the impersonator was a fellow agent—Mr. Kuroki—posing as a curios dealer, revealing the layered deception involved in their mission.
Norvel’s mission is critical: he aims to gather intelligence from Madame Delacour regarding when the French fleet will return to port. Along the way, Norvel takes Delacour and Venables to a variety show featuring Fabian the Great, a ventriloquist who secretly leads the gang of saboteurs. This gang includes characters like Hakim, Captain Hawkins, Danforth, and Norvel himself. Interestingly, Danforth, played by [John Carradine], is actually a British Secret Service agent who goes by the name Richard Burke—highlighting the complex web of identities among these characters.
The story intensifies as Mr. Moto listens in on their conversations and narrowly escapes capture. Moto’s keen intelligence and resourcefulness help him slip away from danger. Meanwhile, Fabian starts to suspect that Kuroki could be Mr. Moto, adding another layer of suspicion. Fabian enlists his girlfriend Connie Porter, played by [Virginia Field], who is unaware of her boyfriend's covert identity, to spy on Moto. She witnesses Moto’s visit to the Port Commandant's office, where he learns about the salvage ship The Vulcan, commanded by Captain Hawkins.
As the plot unfolds, Fabian reveals that Danforth is the secret agent working for the British, aiming to sabotage the French fleet and incite conflict between France and England. Fabian's plan is diabolical: he intends to blow up the French ships and pin the blame on the British. To execute this, he lures Burke (Danforth) to The Vulcan and traps him inside a diving bell, causing his death. Norvel, aiming to complete his mission, brings back crucial information to Fabian at the theater.
Connie, overhearing these sinister plans, tries to alert the authorities but falls under Fabian’s control after he persuades her to stay quiet. As the tension escalates, Hakim attempts to kill Mr. Moto with a bomb, but Moto survives and pursues Hakim to a warehouse. An intense fight ensues, leading to Moto and Venables being tied up and thrown into the ocean. Nonetheless, Moto's cunning allows him to escape underwater, where he frees Venables, who then goes to inform the police.
The climax reaches a boiling point when Fabian prepares to trigger the explosives intended to destroy the French fleet. However, Mr. Moto intervenes, detonating the charges prematurely and ending Fabian's plans. In the chaos, Moto fights with Fabian, and Connie intervenes by shooting Fabian, bringing him down. Eventually, Moto uncovers Fabian's dummy, revealing the saboteur's true intentions, yet he chooses not to disclose which country was behind the plot, emphasizing the delicate balance of espionage and diplomacy that underpins the entire story.
Throughout this tale of espionage, deception, and heroism, Mr. Moto remains the quintessential hero—a master of disguise and cunning, working tirelessly to prevent an international conflict. The story showcases a captivating mix of action, intrigue, and subtle political commentary, all set against the evocative backdrop of the port city of Port Said.
