Banker Georges Robin and his fiancé Marie meet the mysterious Dr. Muller, who introduces himself as "a friend to all". During a philosophical conversation, Marie comments that Evil can never conquer Truth, but the doctor sets about to prove her wrong. Muller manipulates Georges' best friend, Paul de Veaux, into confessing his unrequited love for Marie. This revelation brings the couple's impending marriage to a halt and throws Georges into a suicidal depression. When Marie discovers that Muller is behind a plot to disrupt their lives, she begins to suspect that not-so good doctor may be the Devil himself.

The Devil is the first motion picture for acclaimed English actor George Arliss. Arliss had made his name with the stage version in 1908, so a film adaptation of his first success was a natural for his screen debut. He would have his greatest success after the advent of sound, starring in films such as The Man Who Played God (1932), The Working Man (1933) and The House of Rothschild (1934), as well as becoming the first British actor to win the Oscar (for Disraeli, 1929). Born in 1868, Arliss was one of the oldest actors to continue to find success in the Hollywood of the 1920s and 30s. Co-star Edmund Lowe, here at the beginning of his career, would go on to roles in classics like What Price Glory? (1926) and Dinner at Eight (1933), and in the 1950s would star in his own TV series, Front Page Detective (1951-1952). Also making one of his earliest film appearances is future Academy Award winner Fredric March, who can be seen as an extra during the masquerade ball scene.