Synopsis of original Broadway production (from Wikipedia)
In 1934, the villagers of Transylvania Heights celebrate the funeral procession of the mad scientist Dr. Victor von Frankenstein. However, Inspector Kemp, who has a wooden right arm and wooden left leg, tells the town of the existence of Victor's grandson: Frederick, the Dean of Anatomy at New York's Johns, Miriam and Anthony Hopkins School of Medicine. The village idiot, Ziggy, convinces the other villagers that there is no way a New York doctor would come to Transylvania, thus continuing the celebration ("The Happiest Town in Town").
In New York, Frederick Frankenstein is embarrassed to be a Frankenstein, insisting his name be pronounced "Fronkensteen" and that he is not a madman but a scientist. He teaches his students about the greatest mind of science ("The Brain"). After learning that he has inherited his grandfather's castle in Transylvania, he is forced to resolve the issue of the property. As Elizabeth Benning, Frederick's fiancée, sees him off, it is clear that their relationship is far from physical as Elizabeth enumerates all the lustful situations from which she is abstaining ("Please Don’t Touch Me”).
Arriving at Transylvania Heights, Frederick meets the hunchback Igor (pronounced "Eye-gore"), the grandson of Victor's henchman, who is overjoyed to meet Frederick. Igor tries to convince him to continue in his grandfather's footsteps ("Together Again"); he has already hired the services of Inga, a yodeling lab assistant with a degree in Laboratory Science from the local community college. After a wagon ride to Castle Frankenstein ("Roll in the Hay"), they meet the mysterious Frau Blucher, whose spoken name frightens the horses.
Once inside the castle's main living room, Frederick falls asleep reading Rebecca of Sunnybrook Farm and dreams that his grandfather and ancestors encourage him to build a monster ("Join the Family Business"). He is awakened by Inga, and they, followed shortly by Igor, find the secret entrance to his grandfather's laboratory behind a book case by following eerie violin music. They discover the mysterious violin player to be Frau Blucher, who tells of her past with the late Victor for whom she was more than just a housekeeper ("He Vas My Boyfriend"). After reviewing his grandfather's notes, Frederick decides to carry on the experiments in the reanimation of the dead and asks Igor to find a large corpse as well as the brain of a scholar. The villagers gather at the local town hall for a meeting and are instructed to be on the lookout for grave robbers, as Frederick and Igor go through the town with their corpse ("The Law"). Igor returns with the brain, but drops it, secretly replacing it with another. Frederick creates the creature ("Life, Life"), who goes on a violent rampage shortly after waking. The doctor is dismayed to find that Igor had provided a different brain whose name he recalls as "Abby Normal".
Inspector Kemp and the townspeople come to the castle to investigate, pretending to welcome Frederick ("Welcome to Transylvania"). Frederick and his employees try to stall the villagers ("Transylvania Mania") while Frau Blucher frees the Monster without letting Frederick know. Panic ensues as the monster breaks free from the stage and runs through the audience.
The town begins to search for the Monster, with Frau Blucher trying to bring him back with music from her violin, but to no avail ("He's Loose"). Inga talks to the anxious doctor ("Listen to Your Heart"). Frau Blucher and Igor find the two suspended on the platform, completing what Igor refers to as "an experiment in female anatomy".
Elizabeth arrives unexpectedly in Transylvania with a large entourage ("Surprise") and finds Frederick and Inga, both in a state of undress, who tells her that no funny business was taking place. Meanwhile, the Monster finds a blind hermit named Harold after breaking through the wall of his house ("Please Send Me Someone"). Eventually, after Harold accidentally pours hot soup into the Monster's lap and lights his thumb (mistaking it as a cigar), the Monster is pained into another wild rampage and leaves. Frederick locks himself into a room with the Monster, and after overcoming his fears he tells the Monster that he is a handsome man who is loved and will be hailed by all ("Man About Town").
The Monster is presented at the Loews Transylvania Theatre, now dressed as a gentleman, first walking on command, and then dancing to Irving Berlin's "Puttin' On the Ritz". While taking his bow, the Monster is scared when some stage lights explode. Elizabeth is kidnapped by the creature and is taken to a cave, where he forces himself on her. However, she is now seeing a different side of the Monster and discovers what she has been yearning for in her life ("Deep Love"). Luring the Monster back to the castle by the music of a French horn, Frederick attempts an intelligence transfer, but the Monster does not wake, and to make things worse, Inspector Kemp and the angry villagers (believing that Elizabeth has been killed by the Monster) break into the castle and bring Frederick to the gallows. The doctor is hanged after finally accepting his family name ("Frederick's Soliloquy").
The Monster returns, not only able to speak articulately but also using his newly transferred medical skills to discover that Frederick is not dead, but merely unconscious and is able to revive him. Just as the crowd is about to re-hang Frederick and the Monster, Elizabeth arrives with a Bride of Frankenstein hairdo. The Monster proposes to Elizabeth ("Deep Love" (Reprise)) and a happy ending is ahead for all as the moon shines high on the newly engaged Doctor and Inga ("Finale Ultimo").