It's 1912 and Greece is beset by war and pestilence. As his troops bury their dead after another bloody battle, stern General Pherides (Boris Karloff) goes to visit the grave of his wife, buried on an island nearby. He's horrified to see her tomb has been looted and learns grave robbers are to blame for the desecration but there is worse news to come: plague has come to the island.
The doctors are powerless but perhaps the sickness has another cause. Could it be that a 'Vorvolaka' - a vampiric demon - is at large on the island? And is there anything that can stop it?