Years later, Frankenstein, now going by the alias of Dr. Stein, has become a successful physician in Carlsbruck, catering to the wealthy while also attending to the poor in a paupers' hospital. Dr. Hans Kleve, a junior member of the medical council, recognises him and blackmails him into allowing him to become his apprentice. Together with Karl, the hunchback who facilitated Frankenstein's escape, Frankenstein and Kleve continue with the Baron's experiment: transplanting a living brain into a new body—one that isn't a crude, cobbled-together monster. The deformed Karl is more than willing to volunteer his brain, thereby gaining a new, healthy body—particularly after meeting the new assistant at the hospital, the lovely Margaret. The transplant succeeds, but when the excited Dr. Kleve tells Karl that he will be a medical sensation, Karl panics and convinces Margaret to free him. Kleve notes that the chimpanzee that Frankenstein transplanted with the brain of an orangutan ate its mate and worries about Karl, but his concerns are brushed off by Frankenstein. Karl flees from the hospital and hides in Dr. Stein's laboratory, where he burns his preserved hunchback body. He is attacked by the drunken janitor, who takes him for a burglar, but manages to strangle the man. Frankenstein and Kleve discover Karl is missing and begin searching for him. The next morning, Margaret finds Karl in her aunt's stable. While she goes to fetch Dr. Kleve, Karl experiences difficulties with his arm and leg. When Kleve and Margaret arrive, he is gone. At night, he ambushes and strangles a local girl. The next night, he rushes into an evening reception. Having redeveloped his deformities,
