While salting an old castle with gems to entice a shady buyer, Tony and Timmy stumble across a den of thieves using the castle to stash stolen loot. They escape in a car containing a sack of the money. Complications ensue.
Marcel (Charles Boyer) is set to perpetrate an art swap on stingy businessman Amos Cavanaugh (Broderick Crawford). But Cavanaugh has put a twist to the con by unexpectedly donating his Rembrandt to the SF Art Museum. Fake copies cloud the investigation while they search for the real Rembrandt. The museum and Cavanaugh wish to work the dealings on their own, keeping the press and the police out of it; when several step forward claiming they have the original and asking for a ransom. Can Marcel and the Rouges make everything right by finding and delivering the real ...
When ruthless and unusually wary tycoon Gregg Roberts tries to take advantage of Tony's friend Peter Stewart, Tony devises a scheme to have Roberts invest in a venture involving a new scientific method that produces gold.
Posing as an African safari guide, Tony takes the lead in teaching greedy and abrasive businessman Champion a lesson for cheating safari guide Rutledge by selling Champion a diamond mine that the family does not own.
Marcel and Timmy at Genoa to meet fellow con artist Armand who says a ship's cargo contains an unspecified item of value. After Armand is murdered, the two open shop with his widow to lure someone to identify the object.
Tony as the son of an ostracized MacBride arrives after Amelia has murdered the father. Tony upon learning that his alter ego has been named sole heir renounces the inheritance but asks for swamp land which he later suggests holds oil.
When Timmy's old school friend is murdered in France, he learns that the old friend was just not a painter but an intelligence agent at which time Timmy and Marcel decide to go Paris to investigate what appears to be unfinished espionage.
In exchange for overlooking Timmy's crime, Inspector Briscoe persuades Marcel and Timmy to undertake the dangerous mission of replacing a fake hand of a statue with the real one long ago stolen to prevent Mme. Ka using the theft to organize a coup.
Girlie magazine tycoon Guy Gabriel wants to foreclose on Lady Brayford to acquire her rare book collection. The Rogues devise a scheme using an old Timmy forgery to save Lady Brayford from foreclosure.
Albert Sorel is pushed from a Swiss ski lift by two men but daughter Madeleine, Tony's friend, is informed by police her father died 20 years ago. In France Sorel's old friend Duval confirms this as two 'German cousins' appear in town.