A wealthy widow, the Countess La Rosa Capellini (Raspani Dandolo), believes that the soul of her late husband Archibaldo has entered her Siamese cat, and there demands that the feline be treated like a prince. As long as Archibaldo the cat is looked after property, the widow declares that when she dies she will leave her estate to her servants: Ciccio La Capra the butler (Ciccio Ingrassia) Gina the maid (Ivy Holzer), and Franco Pipitone the general dogsbody (Franco Franchi).Tasked with taking the cat for walks, the dim-witted Franco and Cicco frequently lose the animal, but is usually comes back on its own. These incidents occur so frequently the local businesses have worked out for a scam: whenever Franco and Ciccio turn up looking for the cat, the butcher claims that it has eaten his sausages, the delicatessen owner claims it has stolen salamis, and Ciccio duly stumps up the widow's cash.When the Countess dies, the notary informs the servants of the good fortune: unfortunately Archibaldo has gone missing, this time seemingly for good. Meanwhile at a neighboring mansion the Count and Countess De Vita are appalled to discover that a prestigious dinner party they are hosting has thirteen guests. The Countess is extremely superstitious so when Ciccio arrives, searching for the cat Archibaldo. He is greeted effusively and invited to dine. However one of the guests, a Dutchess, recognizes him as a servant for the late Countess La Rosa Capellini and refuses to eat at the same table. The Dutchess and her husband leave in disgust, various guests cancer or arrive unexpectedly and chaos ensues. Meanwhile, Franco as picked up a gold-digger in the form of Antonietta, the Count's maidservant, who becomes very flirtatious when she hears of the pending inheritance.The next morning, Gina spots Archibaldo in the grounds of the nearby Embassy of the (fictitious) Republic of Guaramy, which is currently hosting a visit from His Excellency, Prime Minister Ordonez of Guaramy. In attendance is Joe Smith (Daniel Vargas) an American CIA agent, Ordonez secretary Mr. Martinez (Andrea Scotti) and an inept Italian police chief, Commissioner Proietti (Enzo Le Torre). When Franco and Ciccio claim to have seen "the cat" on the premises, Smith and Proietti mistakenly assume that two idiots are referring to a notorious criminal know as 'The Cat' whom they believe plans to assassinate Ordonez. Thinking that Franco and Ciccio are somehow involved, Smith has them bugged and orders Proietti to arrest everyone whom they talk to. Soon, all of the local business-folk who defrauded the widow are locked up.Meanwhile, Martinez, who is plotting against his boss, passes photos of Franco and Ciccio whom he perceives as a threat, to a group of local hoods who undertake to kill them. However, it is 'the Cat' himself (Ivano Staccioli) who shows up and deals with the situation, using Gina to lure Franco and Ciccio back to the widow's house and tying them to all chairs in an upstairs room, with a time bomb on the dresser. The Cat tries to leave, but realizes that his car keys are missing; they have been stolen by Archibaldo who is attracted to the furry key ring. Franco and Ciccio mange to roll the bomb to the edge the window balcony and Archibaldo finished the job by nudging it off the ledge into the assassin's open-topped car below. The Cat retrieve his car keys and tries to drive away, when the bomb explodes and kills him.In the final scene, Franco, Ciccio and Gina, having claimed the widow's inheritance, are left to enjoy a life of luxury in the widow's mansion.