The opening scenes of this film really grabbed me. The story centers on a meticulous police officer, "Patou" (played by Jack Lemmon), who finds himself unexpectedly assigned to a Parisian district known for prostitution. It’s there he meets the titular character, a prostitute (Shirley MacLaine) and her pet dog. Suspicious of what's happening, he immediately requests a raid on the hotel where she works. This proves to be a misjudgment! Not only does one of his superiors benefit from the situation, but he also loses his job as a result. He then spends most of his time at "Moustache’s" café across the street from her workplace and grows increasingly annoyed that the woman he's developing feelings for continues to work. So, he comes up with an elaborate scheme: pretending to be a British lord in order to win her over exclusively. For a while, this plan works—funded by loans from a newfound friend—but when "Moustache" demands repayment, “Patou” is forced to take on night shifts at the nearby meat market. His hectic lifestyle soon causes problems with "Irma." Ultimately, he realizes his charade can’t go on and pretends to commit suicide. However, the astute "Insp. Lefevre" (Herschel Bernardi) has a different perspective, and “Patou” ends up in jail for murder! Now, he must escape, clear his name—in a rather unusual way—and hope that his girlfriend hasn't grown tired of all this craziness and found someone else. MacLaine gives it her all – dancing, flirting, and fully embracing the role – and she’s thoroughly enjoyable to watch. I’ve never been a huge fan of Jack Lemmon’s comedic performances, but here he uses her talents along with a sharp script by Billy Wilder and IAL Diamond to develop an interesting character that mostly avoids becoming overly silly as the story moves from moments of brilliance to absurdity. It does feel slow at times, and the unbelievable elements begin to take over then too, but it recovers well for a final thirty minutes of peculiar, entertaining cinema with an unexpected ending.

Source on TMDB