Mystery Island: Winner Takes All

Louis and August Siever, twin sons of a German father and American mother, are traveling through Europe when war breaks out. August joins the Kaiser's army, while Louis, a loyal American, is trapped in Berlin for a year while he tries to prove his citizenship. After a violent confrontation with Louis, August steals his brother's passport and leaves for New York City with Gerda Anderson, a German spy. Louis also returns to the U.S., and sometime later is invited to a weekend party on Long Island by his wealthy friends, the Waynes. When August and Gerda learn of the event, they rent a nearby house and invite all of the Waynes' guests, including Louis, to a "mystery" party. Upon their arrival, the women are held prisoner and ransom notes are sent to their husbands via carrier pigeon. Shirley Wayne and Louis track down and are captured by the kidnappers. Meanwhile, Mortimer Eddington, an amateur detective, devises a method to trace the pigeons back to the house. Before Shirley and Louis come to harm, police officers arrive and demand the Germans' surrender.

Scotland Yard's Room 40 was instrumental in Allied victory during WW1, but has been compromised in the decades since, a killer in their midst.

Reporter Hela Martinic returns home from Australia to wartime Zagreb, only to find herself investigating the mysterious death of an old friend, Vera Kralj.

Reporter Dallas Dayle and FBI agent Bob Grayson hunt an escaped German agent.

During WW2, a Royal Navy Commander stumbles upon a murdered woman and discovers a network of Nazi spies and Fifth-Columnists.

Kay Murdock (Lynn Bari) strolls into the Dixie Bar in Shanghai on November 1, 1941 and asks the bartender for a letter addressed to Captain Larsen, and is referred to Roy Bonnell (Preston Foster), the manager of this combination bar and gambling house. He refuses to turn the letter over to her and she steals it. Bonnell later recovers the letter which contains a coded note. Kay reveals she is an agent of the British Secret Service. Bonnell, a fugitive from American justice, says he will turn over the note to the highest bidder. When he approaches the Japanese, they seize him but he escapes, after learing that the note was part of an alarm for Japanese fifth columnists everywhere after the attack on Pearl Harbor that has just been set in motion.