In the nineteen century, in London, dedicated housemaid Mary Reilly (Julia Roberts) is part of the staff under the command of the butler Mr. Poole (George Cole), who works for Dr. Henry Jekyll (John Malkovich).
Mary is a traumatized woman that was abused by her father when she was a child, and is very devoted to Dr. Jekyll.
One day, he gathers Mr. Poole and the servants in a room and tells them that his assistant Mr. Edward Hyde will be working in his laboratory with free access to the house.
Mary Reilly and her mates are unsuccessful to see the mysterious Mr. Hyde.
Dr. Jekyll trusts on Mary Reilly and she helps him, delivering letters to the notorious Mrs. Farraday (Glenn Close), who owns a brothel, to clean the mess that Mr. Hyde makes in the city.
Mary Reilly is seduced by the educated Dr. Jekyll and by the reckless and violent Mr. Hyde.