While delivering a new design to her boss, Patience overhears a plot to sell defective beauty products that initially make human skin look younger and prettier; if the product is not used over a long period of time, however, the skin begins to decay. Unfortunately she is spotted at the scene and attempts to flee into a set of water conduits. The pipes are flooded by her pursuers, and she is flushed into the open water and drowns.
After being murdered, she is brought back to life by the cat she saw earlier, because the cat was moved by the fact that she risked her own life for it. When she wakes up, she is transformed into Catwoman, a warrior with the force of a cat, who prowls the night in search of justice. Her behavior becomes cat-like, and she gains heightened reflexes, senses, and physical power.
Determined to discover why she was murdered (having forgotten the events that occurred the night before), Patience re-learns about the beauty product and when she goes to the factory where the product is made, she finds a scientist who protested against the product's release murdered. Before she can investigate further, however, the night guard spots her and sounds the alarm. Patience quickly flees the factory. She then informs her boss's wife, Laurel Hedare (Sharon Stone), about the plan and asks her to keep an eye out for anything unusual.
Catwoman then heads to the opera house where her boss, George, is attending a play with another woman. She confronts him about the product, but he doesn't know about it's toxic after-effects. The police arrive and chase Catwoman, who is able to escape by cutting off the power.
Patience and Lone then go out on a date at a sushi resturant, where they talk about Catwoman. When they leave, they go to Patience's home and make love. Lone then leaves later, after he finds one Catwoman's fake claw nails.
Later, Laurel contacts Catwoman, and tricks her into entering a room with Patience's brutally murdered boss lying on the floor. Laurel then calls the police after pushing a gun into Catwoman's hand. As she flees the house, Catwoman realizes that Laurel was the one who insisted on the product's release and murdered the scientist.
The prints on the gun were matched up with those of Patience, and she was taken into custody by Lone. That night she is able to escape from her jail cell, however, by squeezing through the bars like a cat.
Meanwhile, Lone goes to Laurel, while she holds a press conference for the beauty product and a tribute to George. They go to her office and talk, and during their conversation, Laurel lets slip that she was the murderer of the scientist and her husband. But, before Lone can arrest her, she pulls a gun and shoots him in the arm. Catwoman then arrives, and rescues Lone just as Laurel is about to finish him off. After taking out her henchmen, Catwoman confronts Laurel, and they fight, though Laurel's face is now like "living marble" from using the product for so long. Catwoman slashes her face and causes it to rip. Laurel is horrified by her reflection in a mirror and falls out of a window to her death, although Catwoman attempts to rescue her.
At the end of the movie Patience sends a thank you note to the woman who gave her the cat mask, and a letter to Detective Lone, saying good bye and thank you and walks off into the night, happy with her new independence.