Léopold, valet de chambre de l'avocat général de Royssac, se met à étudier le code pénal et devient, pendant ses congés, juge dans un tribunal du « milieu ». Ses décisions sont reconnues sans appel. Léopold tombe amoureux d'Agnès, fiancée au docteur Ventoux, qui a un double visage et devient « Le chat » quand il joue les gangsters. Léopold aidera « Le chat » à réussir le hold-up du siècle, s'il reste libre de courtiser Agnès. « Le chat » ne joue pas le jeu. Une bagarre entre la bande de Léopold et la bande du « chat » éclate. Force reste à la loi.
Hal McLeavy, le fils d'un directeur d'hôtel dans une station balnéaire anglaise, et son ami Dennis cambriolent une banque voisine de l'entreprise de pompes funèbres où travaille Dennis. Ils cachent le butin dans un cercueil. L'inspecteur Truscott, chargé de l'enquête, les soupçonnent rapidement. Pendant ce temps, M. McLeavy, le père de Hal, est courtisé par Fay McMahon, l'infirmière qui a soigné sa femme pendant ses dernières semaines de vie. L'inspecteur Truscott s'intéresse aussi à Fay McMahon, car il est sûr qu'elle a tué plusieurs de ses anciens maris et qu'elle pourrait avoir empoisonné la mède de Hal.
1947 à Hollywood. Lou Anglich échappe à une filature en frappant son poursuivant avec sa valise. Lorsque Leslie C. Tucker, un détective privé anglais, revient à son bureau, il trouve Anglich, qui le charge de retrouver a fille Anna, placée dans un orphelinat 29 ans auparavant. Anglich dit à Tucker qu'il a beaucoup d'argent et qu'il veut le donner à sa fille avant que ses "associés" le retrouvent et le tuent...
Gold-digging chorus girl Mary (Carole Lombard) marries the head of a bootlegging syndicate, gangster "Shoots" Magiz (Nat Pendleton), but the illegal liquor business goes down the drain when Prohibition is repealed, and Shoots is knocked off by rival Daniel Dingle (Sam Hardy). Mary, looking for a new sugar-daddy, hooks up with Dingle, and when Dingle is removed from the scene by Mickey "The Greek" Mikapopoulis (Leo Carrillo), transfers her attention to him in return for a "trust fund". All the time, fast-talking straight-shooter Jimmy "Office Boy" Burnham (Chester Morris), Shoots' former bodyguard and errand boy, has looked after Mary, passing her advice and snappy remarks whenever they're needed. In the end, Mary and Office Boy end up together, but only after "Merry Widow Mary" gives away all the dirty money she was given.
Tout juste sorti de prison, "Pinky" Green est déterminé à aller dans le droit chemin et, comme il est un électricien qualifié, il est engagé par une société appelée Global Group Security. Cette entreprise l'envoie travailler au système de sécurité de l'Atlantic and Pacific Bank dans le quartier de Mayfair. Un certain Ivan le Terrible le fait alors chanter pour qu'il les aide à dévaliser la banque de Berkeley Square.
Retired detective Charlie Chan is asked for his help by the San Francisco police to solve a new series of murders. But this time his usual sidekick, Number One Son, has been replaced by Lee's own son, Lee Chan, Jr.
Against her wealthy industrialist father Albert's wishes, young Virginie (Brigitte Bardot) marries dentist Hervé Dandieu (Henri Vidal). After three months, all passion has disappeared, and after an argument, Hervé leaves the house for a drink at a club. There, he is seduced by Anita Florès (Dawn Addams), a red-headed dance instructor. Unbeknownst to him, Anita is a scam artist who has sent her boyfriend Léon (Serge Gainsbourg) to photograph her in companionship with Hervé. Although Hervé eventually decides to stay faithful to his wife, Léon is able to take some pictures of their intimate moments.
In London, a gang of criminals from Australia led by Jack Coombes (Bill Kerr) impersonate policemen to carry out robberies. Local gang leader "Pearly" Gates (Sellers), who operates from the cover of a French couturier, finds his takings cut severely, and blames rival crook "Nervous" O'Toole (Bernard Cribbins). When it emerges that they are both being scammed by the same gang, they join forces, along with Lionel Jeffries' Police Inspector "Nosey" Parker, to bring the so-called "I.P.O. mob" (I.P.O. - Impersonating a Police Officer) to justice. Nanette Newman provides the love interest, the ubiquitous John Le Mesurier plays a senior policeman, and a young Michael Caine has a small and uncredited role as a young PC. Other uncredited roles include John Junkin (Maurice), Dennis Price (Educated Ernest), Cardew Robinson (Mailman), Dick Emery (Man in Flat 307), Mario Fabrizi (Van Driver), John Harvey (Police Station Sergeant), Harold Siddons (PC in Basement Garage), Jack Silk (Police Station PC), Derek Guyler (non-speaking PC at Scotland Yard), Gerald Sim (Airfield Official) and Marianne Stone (Woman in Front Row at Gangsters' Meeting).
In the mysterious metropolis of Rain City, a former policeman, Hawk, is out of prison after serving eight years on a murder rap. He returns to his former hangout, Wanda's Cafe, run by his former love, Wanda.
In Italy in the Sixties, a gang of American thieves arrive in Naples to steal the famous Treasure of San Gennaro. However the Americans do not know how to move in the picturesque town. For the customs of the natives are too weird and incomprehensible to them. So the two men and the girl (the gang members) go to a prison, following the advice of a friend. There he would find the man who would have done in their case. It is a certain Don Vincenzo, a very famous in the city for his theft. He however, since it is known by everyone there, is treated in the prison as a gentleman by the guards with all possible facilities. The Americans, when they see this type of treatment, impossible in a country like them, remain quite stunned. Don Vincenzo warmly received them and advises them to go to Naples to look for a certain Armandino Girasole, said "Dudù". He, a young thief by profession, would help them steal the treasure of San Gennaro, fortunately not mentioned by the Americans to Don Vincenzo. The Americans, keeping secret the purpose of theft, meet Dudù and agree with him.
An organized crime wave strikes across Europe. Suspecting a mole within Scotland Yard, the Prime Minister brings Clouseau in to solve the case. Clouseau foils two assassination attempts but is subsequently kidnapped. The gang uses him to make masks of his face which they later use to commit a series of daring bank robberies across Switzerland. Eventually, Clouseau foils the plot and unmasks the traitor within the Yard.