A pair of bizarre murders occur wherein the victims are drained of their rare blood type. Reporter Walter Garrett consults with his friend Dr. Mike Rhodes which leads them to Rhode's former mentor, hemotologist Dr. Francis Flegg. Flegg is initially unhelpful but when Garrett and Rhodes notice a striking resemblance between Flegg's strange assistant, Marshall Quesne and the late Dr. Maurice Xavier, they confront Flegg. Flegg admits that he used scientific methods to bring Xavier back from the grave and employed a synthetic blood formula to sustain his life. However, the formula is unstable, therefore, Quesne/Xavier must seek out human victims with a rare blood type featured in the formula in order stay alive.