Baron Frankenstein blackmails a brother and sister into helping him with a brain transplant.

Baron Frankenstein, observed performing an illegal brain transplant, flees to Altenburg where he finds a room in Anna Spengler's boardinghouse. When Frankenstein discovers that Anna's fiancé, Dr. Karl Holst, is stealing drugs from the asylum where he works, he blackmails Holst into abducting Dr. Brandt, now a patient but formerly Frankenstein's colleague and an expert on brain transplants. Brandt dies of a heart attack, however, before he can divulge his secrets. On his own, Frankenstein transplants Brandt's brain into the head of Professor Richter, a doctor at the asylum. When Brandt awakens with Richter's body and goes to Anna for help, she becomes terrified and stabs him. After Brandt staggers away, Frankenstein murders Anna and goes after Brandt, who has gone completely mad. Frankenstein finds Brandt, but the madman sets fire to his own house, destroying himself and Frankenstein.