Curse of the Pink Panther

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In Lugash, the fabled Pink Panther diamond is stolen. A mysterious woman looking to procure the priceless gem has a tete-a-tete with a man regarding price. Suddenly, Clouseau (having disappeared inexplicably on a plane flight in the previous film) bursts in. The woman shoots the man, then points the gun at Clouseau. His fate is a mystery. Meanwhile, his former superior, Chief Inspector Charles Dreyfus (Herbert Lom), is pressured to oversee Operation Paragon and utilize Interpol's fictitious Huxley Huxley 600 computer Aldous to find the world's greatest detective to solve the crime.
What the world at large does not realize is that Clouseau was actually an inept fool whose cases were solved more through luck than actual detective genius, and that his accident-prone incompetence led Dreyfus to a series of nervous breakdowns. Anxious never to see or hear from his nemesis again, Dreyfus sabotages the computer to select the world's worst detective. This turns out to be Sergeant Clifton Sleigh (Ted Wass), an incompetent officer of the New York Police Department.
Sleigh, who is descended from a long line of cops, sees the case as an opportunity to prove his worth. Dreyfus and his long-suffering assistant, Sergeant FranÃ§ois Durval (AndrÃ© Maranne), soon find that the sabotage has worked a bit too well: while slightly more intelligent and capable, Sleigh is just as clumsy as Clouseau. When Sleigh meets Dreyfus for the first time in his office, Sleigh trips over his own feet and knocks Dreyfus into his wheeled office chair, which rolls out onto the balcony â and sends Dreyfus falling three stories into a pond below, breaking his left leg. Sleigh visits Dreyfus in the hospital to apologize, but accidentally ends up hurting Dreyfus more by falling over the hospital equipment holding Dreyfus's leg.
As he sets out on the case, Sergeant Sleigh encounters many people who prefer Clouseau not return: these include the Inspector's former manservant, Cato (Burt Kwouk), who attacks Sleigh when he breaks into the Clouseau Museum Cato now operates; Dreyfus, who attempts to kill Sleigh numerous times like he tried to kill Clouseau; and Bruno Langlois (Robert Loggia), the mafia boss from the previous film. Langlois orders several assassination attempts on Sleigh, but the detective's bumbling nature allows him to survive. Ultimately, Langlois, along with his henchmen (including Mr. Chong from Revenge of the Pink Panther) have a final showdown with Sleigh in a dark alley in Valencia, Spain, during Carnival. Juleta Shayne (Leslie Ash), an employee of the enigmatic Countess Chandra, comes to Sleigh's rescue and manages to defeat Langlois and his thugs in street combat.
Sleigh also meets Sir Charles Lytton (David Niven), who is now married to Clouseau's former wife Simone (Capucine), and is accompanied by his nephew George (Robert Wagner). Sir Charles was the notorious jewel thief known as "the Phantom," though only Clouseau was convinced of this. The Phantom would steal items of jewelery and leave behind a monogrammed white glove.
Eventually, Sleigh's trail leads to a health spa run by Countess Chandra (Joanna Lumley). There he meets famous British film star Roger Moore, who speaks with a rather odd French accent and falls about all over the place. Seeing a photograph of the Inspector, Countess Chandra tells Sleigh that Clouseau visited her several months ago, but claimed his name was Gino Rossi (the thief who stole the diamond in the last film and was seen fencing it to Countess Chandra at the start of this film when the real Inspector arrived on the scene). She recalls he was looking for a good plastic surgeon and she recommended one.
Sleigh concludes, erroneously, that Clouseau stole the Pink Panther diamond, underwent plastic surgery, and changed his name to Gino Rossi. The real jewel thief's body was found washed up on shore after he was shot to death. It is believed that Clouseau was killed for the diamond. Anxious to be rid of Sleigh, Dreyfus announces that Sleigh has solved the mystery and officially closes the case, though it is clear that Dreyfus does not believe that this is what happened. In a final irony, as Dreyfus sets fire to Gino Rossi's photograph â happy to be rid of Clouseau once and for all â he accidentally sets fire to his office. Sleigh runs in and attempts to put out the fire with a hose, only to accidentally hit Dreyfus with the water, the force of which pushes him onto his balcony and Dreyfus again falls three stories into the pond below, sending him most likely back to the insane asylum.
Film star Roger Moore was, in fact, Clouseau after very extensive plastic surgery. Clouseau has become Countess Chandra's lover and partner in crime. When Clouseau and Chandra open her hidden wall safe to admire The Pink Panther, they discover they have been robbed, and a white monogrammed glove has been left behind. "Swine Phantom!" mutters Clouseau, knowing only too well who is responsible for the theft. In the final scene, Sir Charles, Simone, and George are sailing away on board their yacht with The Pink Panther jewel, which Simone has stolen.
In a post-credits scene, the animated Pink Panther is shown stealing the Pink Panther jewel. Realizing it's heavy, he slips out of the shot and drops the diamond offscreen, shattering it; the credits roll shortly afterwards.

Question: Who does Sleigh think stole the the Pink Panther diamond?
Answer: Clouseau