The film begins with Daniel Harbour, a young and ambitious lawyer, who is recruited by a top law firm in Milan. Daniel is thrilled to work with the firm, but soon discovers that the firm's top client is a mysterious and charismatic figure named Lucifer (Al Pacino). As Daniel becomes more involved in the case, he begins to suspect that Lucifer is, in fact, the devil. Despite his reservations, Daniel becomes increasingly drawn into the case and finds himself questioning his own faith and morality.
The film's success can also be attributed to its strong performances, particularly from Al Pacino and Keanu Reeves. The film's visuals and special effects were also widely praised, and its depiction of hell and the devil's lair has become iconic.
Another theme of the film is the nature of faith and doubt. Daniel's journey is a classic example of a spiritual crisis, as he grapples with his own faith and the existence of God. The film raises questions about the role of faith in modern life and the difficulties of maintaining a strong spiritual foundation in a secular world.