Aga Ben Dragore, a knife-wielding, enigmatic Egyptian Arab, is seeking a sacred jewel which has been stolen from an ancient tomb. The thief tells him that he sold it to Professor Morlant, a fanatical Egyptologist who fervently believes in the pagan power of the ancient Egyptian gods. Dying from a mysteriously disfiguring ailment, Morlant entrusts his faithful manservant to bandage the jewel in his hand and warns him of dire consequences if his dying wishes aren't carried out. After his burial in an Egyptian-type tomb on his estate, an anonymous robber steals the precious stone from the corpse. Although the ghastly-looking dead man rises at the next full moon to seek revenge, neither he nor the audience know which member of the household possesses the powerful jewel. A dying professor of Egyptology (Boris Karloff) asks to be buried with a valuable jewel known as the Eternal Light, which he believes will grant him immortality in the afterlife. When his butler (Ernest Thesiger) steals the jewel from his tomb, Karloff returns from the dead to seek revenge.
