The film was not originally written to include Clouseau, but was an adaptation of a stage play by Harry Kurnitz adapted from the French play L'Idiote by Marcel Achard. As Blake Edwards and future The Exorcist creator William Peter Blatty began work on the script, they decided the story would be a good vehicle for the Clouseau character, and rewrote the script around the new premise. The film was released only a few months after the first Clouseau film, The Pink Panther.
As Clouseau continues to bungle the case, Commissioner Dreyfus becomes increasingly agitated, resulting in his accidentally cutting off his thumb and stabbing himself with a letter-opener. An anonymous figure starts attempting to kill Clouseau, but ends killing a doorman, two cafe customers, and a Cossack dancer, thus leading to an explosive ending as all the suspects in the case – Ballon, his wife, and all of the servants were murdering each other for having love affairs, except Maurice, who was a blackmailing butler – are blown up as they attempt to escape in Clouseau's car. The anonymous bomber is revealed to be Commissioner Dreyfus, who has been driven mad by Clouseau's blunders, and, in trying to kill him, has accidentally murdered the real killers.
The bumbling detective of the film (and the Pink Panther films in general), with an exaggerated French accent and an incredibly clumsy manner. He is somewhat short-sighted, comes to conclusions that would by others be thought irrational, has a lucid visual memory, and tends to be rather literally minded. Clouseau continually causes Dreyfus frustration, and this is the first of many times he drives his superior literally insane over the course of the series. He also tends to blame his blunders on others (for example, after falling into a fountain, he comments that he fell in because "...my idiot driver parked too close to the fountain").
Dreyfus is Clouseau's boss, first seen in this film. He slowly goes mad over the course of the film, and by the end he makes several attempts to kill Clouseau (the first of many examples, which result in Dreyfus being consigned to an asylum several times over the film series).
Maria, the beautiful maid for the Ballon family, is framed by the killers for the murder in question. Like Clouseau, she has an unfortunate aptitude for being in the wrong place at the right time. Towards the end of the film she begins a sexual affair with him.
Kato is Clouseau's servant, trained in the martial arts. Clouseau, suspecting that murderers were trying to kill him, ordered a "training program" with Kato, telling him to attack "wherever and whenever I least expect it." This becomes a running gag throughout this film (and the films in general), as Kato chooses to attack his boss at the most inconvenient times, such as when there is a murderer attempting to kill Clouseau or when Clouseau is in a sexually intimate moment). The resulting fights usually destroy Clouseau's apartment, which is inexplicably rebuilt thereafter. All succeeding films would spell his name "Cato."
Benjamin Ballon (George Sanders)
Ballon is the millionaire at whose house the initial murder takes place. Due to a complex network of affairs between the various residents, the culprits continue murdering people, eventually raising the count to four. The murderers decide to pin the blame on the unsuspecting maid, with whom Clouseau becomes infatuated, forcing the perpetrators to attempt to disappear. Due to a mistake, they are all destroyed.
Hercule LaJoy (Graham Stark)
Inspector Clouseau's silently suffering assistant who is repeatedly asked to look at the evidence of the case by Clouseau and then reprimanded for jumping to the logical conclusion. His name is perhaps a play on the famous Agatha Christie protagonist Hercule Poirot. Hercule believes the chief suspect in the case to be guilty, although Clouseau, who is besotted with her, insists she is innocent and that the evidence points to someone else each time a murder is performed. In the end, Clouseau is serendipitously proved correct.