Young Frankenstein begins with Dr. Frederick Frankenstein, pronounced frahn-ken-steen, grandson of the Frankenstein of monster fame, renouncing his grandfather’s work and pursuing a career as a respectable scientist. One day, however, he stumbles upon his grandfather’s castle, where he finds a journal chronicling the elder Frankenstein’s monster building. Frederick believes it could work, and he sets out to build a new monster with the help of his lackey, Igor, and his lab assistant, Inga.
In order to successfully construct the monster, they have to use large parts; including an enormous schwansztooker, but Igor mistakenly steals an abnormal brain for the monster. The experiment is a success, and the monster lives, but he is a psychopath and mute. The townspeople, wary of the previous monsters, are suspicious of Dr. Frankenstein, now pronounced like his ancestors. When Inspector Kemp investigates the castle, he temporarily placated that there is no evidence of a monster.
Later, something spooks the monster, and he escapes. Outside the castle grounds, he encounters a girl and a lonely blind hermit, but Frankenstein and the crew capture him and teach him to love. They create a musical show featuring the monster, but some fire on stage throws him into a rage. The whole plan unravels. As the monster rampages, he steals Frankenstein’s fiancé, Emily, using his enormous schwanzstooker.
This time, the townspeople form a mob as the Dr. recaptures the monster, and prepares a transplant of conscious from him to the monster. The plan succeeds just as the mob storms the castle laboratory. The monster, now possessing the Doctor’s intelligence, talks the mob down, and everyone is left in peace.
In the end, the monster marries Emily, and the Doctor marries Inga, when it’s revealed that the brain transplant gave the monster his massive intellect, but in return Dr. Frankenstein received something massive from the monster.