Based on a novel by Alexander Dumas, Black Magic stars Orson Welles as the 18th century master hypnotist and charismatic charlatan, Cagliostro. After his mother is executed for supposedly practicing "witchcraft," young Joseph Balsamo is raised by gypsies. Under their tutelage, he perfects his skills performing magic tricks and selling snake oil in the gypsy's travelling caravan show. Eventually Balsamo meets Franz Mesmer, the famous hypnotist, who convinces Joseph he has even greater gifts which could heal the sick. But Joseph chooses a very different path assuming the name Cagliostro and embarking on a vendetta for power over the man who ordered his mother's death.