The Ghost of Frankenstein is a 1942 American horror film directed by Erle C. Kenton. It is the fourth film in the Frankenstein series by Universal Pictures, and the follow-up to Son of Frankenstein. The film's plot follows the previous film's: the Monster (Lon Chaney Jr.) and his companion Ygor (Bela Lugosi) are chased out of town. They go to another small town to encourage the younger son of Dr. Frankenstein (portrayed by Cedric Hardwicke) to continue his father's experiments, so that Ygor can have revenge against his enemies and his brain transplanted into the Monster's skull.
The film was the first in the series with Chaney portraying the monster and was cast one day after the film was announced by Universal. It began production in December 1941 and finished in January 1942. On its release it received praise as being as strong as the previous films from The Hollywood Reporter and The Motion Picture Herald while it received negative reviews from New York Daily News and The New York Times.
The residents of the village of Frankenstein feel they are under a curse and blame all their troubles on Frankenstein's monster. The Mayor allows them to destroy Frankenstein's castle. Ygor finds the monster released from his sulfuric tomb by the explosions. The exposure to the sulfur weakened yet preserved the monster. Ygor and the monster flee the castle, and the monster is struck by a bolt of lightning. Ygor decides to find Ludwig, the second son of Henry Frankenstein, to help the monster regain his strength. Ludwig Frankenstein is a doctor who, along with his assistants Dr. Kettering and Dr. Theodore Bohmer, has a successful practice in Visaria. Bohmer was formerly Ludwig's teacher but is now his envious assistant. Ygor and the monster arrive in Vasaria, where the monster befriends a young girl, Cloestine Hussman. The monster carries her onto a roof to retrieve her ball, killing two villagers who attempt to intervene. After Cloestine asks the monster to bring her back down, the monster returns the girl to her father Herr Hussman and is immediately captured by police. The town prosecutor, Erik Ernst, comes to Ludwig and asks him to examine the giant they have captured. Ygor then visits Ludwig and informs him that the giant is the monster. Ygor implores Ludwig to heal the monster's body and brain. Ludwig refuses, but Ygor threatens to reveal Ludwig's ancestry to the villagers.
At the police station, the monster is restrained with chains as a hearing is conducted to investigate the murder of the villagers. When Ludwig denies recognizing the monster, it breaks free in a fit of rage, and is led away by Ygor. Elsa, Ludwig's daughter, finds the Frankenstein journals and learns the story of the monster. She sees Ygor and the monster in the window, and after breaking into Ludwig's laboratory, the monster kills Dr. Kettering. The monster grabs Elsa, but Ludwig is able to subdue him with knockout gas. Ludwig is examining the monster when it awakens and tries to kill him. Ludwig tranquilizes the monster and then tries to enlist Bohmer's aid in dissecting him. Bohmer refuses, claiming it would be murder. While studying his family's journals, Ludwig is visited by the ghost of his father Henry Frankenstein. The spirit implores him to supply the monster with a good brain. Ludwig calls in Bohmer and Ygor and tells them that he plans to put Dr. Kettering's brain into the monster's skull. Ygor protests and asks Ludwig to use his brain, but Ludwig refuses because of Ygor's sinister nature. Elsa begs Ludwig to stop his experiments, but he chooses to operate on the monster as soon as possible. Ygor tells Bohmer that he should not be subordinate to Ludwig. Ygor promises to help the disgraced doctor if he agrees to put Ygor's brain into the monster.
The police soon arrive at Ludwig's house, searching for the monster. They find the secret room, but Ygor and the monster have fled. The monster abducts Cloestine from her home and returns with her in his arms to Ludwig's chateau. The monster conveys his desire for her brain to be placed in his head. Cloestine does not want to lose her brain, and the monster reluctantly gives her to Elsa. Ludwig then performs the surgery, not knowing that Bohmer has replaced Kettering's brain with Ygor's. In the village, Herr Hussman rouses his neighbors by telling them his daughter has been captured by the monster and that Ludwig is harboring it. Ludwig shows the monster to Erik, but when the monster rises, Ludwig is shocked to hear that it has Ygor's voice. The villagers storm the chateau and the Ygor-Monster decides to have Bohmer fill the house with gas to kill them. Ludwig tries to stop him, but the Ygor-Monster repels the attack and mortally wounds Ludwig. The Ygor-Monster suddenly goes blind. The wounded Ludwig explains that the blindness is a result of the incompatibility between the blood types of Ygor and the monster. Feeling betrayed, the Ygor-Monster then throws Bohmer onto the apparatus, electrocuting him, and inadvertently sets fire to the chateau. The Ygor-Monster becomes trapped in the burning chateau while Erik and Elsa escape, walking out into the sunrise.