Andrea is a shy, retiring woman who longs for the perfect man and finds solace in romance novels. Her co-worker at a drugstore, Carl, asks Andrea out but she spurns him. Another co-worker, Elaine, calls her "the mouse" and tells her there's no such animal as Prince Charming, although there are plenty of other kinds in the dating world. Elaine pops pilfered tranquilizers to help her relax.
One night, a black cat jumps through her window and befriends Andrea. When she comes out from the shower, she finds Guillaume, a suave Frenchman, in her house. She tries to call the police, but the man unsettles her by turning into the cat and back. He seduces her, explaining that he had loved the wrong woman once and her jealous husband had cursed him to be a cat except at night. She believes she's found her Prince Charming.
When Andrea returns to work, she's a changed woman, happy and friendly. In the back room, Carl takes inventory of the drugs and Elaine nervously stashes her tranquilizers in Andrea's purse.
Andrea buys a collar for the cat, but it becomes hostile and scratches her. Guillaume testily explains the collar would be dangerous during his transformation and calls her "a fool of a woman." He insists that she buy revealing lingerie. Elaine finds the lingerie and decides to spy on Andrea.
That night, when Andrea steps out to buy the stronger coffee that Guillaume demands, Elaine knocks on the door. She and Guillaume decide to have a fling while Andrea is out. Andrea returns just in time to see Elaine leaving. Guillaume derides Andrea as a silly, naive woman and says he's leaving. Andrea begs for one more night and prepares his coffee. She discovers Elaine's tranquilizers in her purse and slips them into the coffee. Carl calls and informs her that Elaine was coming to learn her secret. She accepts Carl's offer of a date. She's learned her lesson and won't be fooled anymore.
Guillaume awakes in the morning as a cat again, inside a carrier in a veterinarian's office. Andrea pays to have him neutered.