Ambrosio is an extremely devout monk about 30 years old. He was found left at the Abbey doorstep when he was too young to tell his tale and monks took him and raised him in the monastery. When his constant companion, a novice named Rosario, admits that he is a woman named Matilda, who disguised herself so that she could be near him, begins a struggle in Ambrosio between his religious vows and his personal temptations and ambitions, which leads to abuse, violence, incest and murder.

Matthew Gregory Lewis was an English novelist and dramatist, often referred to as "Monk" Lewis, because of the success of his Gothic novel, The Monk. As a writer, Lewis is typically classified as writing in the Gothic horror genre, along with the authors Charles Robert Maturin and Mary Shelley.