For the sake of convenience, we must assume that everything ugly is evil. Lightning rejuvenates. Sulfur preserves. The obvious solution is dismemberment. But the ghost appears to Ludwig; "How can you destroy my creation?"

A new brain must be placed in the skull. Ludwig hopes this will solve the problem, but we know the monster will still be ugly and, as such, evil. The villagers will shun him. He will grow resentful, go on a rampage. This simple truth is lost on Ludwig. Ygor offers his brain. He wants eternal life, the strength of a hundred men, the power to avenge himself on the villagers who disfigured him. This goes contrary to the idea of making the monster a nicer fellow.

Ludwig is against it.

For his own part, the creature wants the brain of a little girl. He stands in the great room of the mansion, cradling Ludwig's granddaughter, still wrapped in her blankets. He places his hand on the girl's forehead, then touches his own. He wants to be innocent. He wants to be beautiful.

Ludwig is against it.

His jealous assistant performs the surgery in secret. After the procedure, we see the monster talking, hear Ygor's voice from within. "It is I!" he exclaims. "Ygor! And now I will live forever! I will have the strength of a hundred men!" Blood type is a consideration, though. Ygor and the creature are incompatible. The sensory nerves do not function. Ygor cries out, "What good is a body without eyes?" Enraged, he gropes violently for the door, destroys some fancy looking machinery in the process. The joint catches fire and burns. Nothing that is ugly survives.

We do not know what became of the monster's original brain.