Act One

In New York, Frederick Frankenstein is ashamed to be a Frankenstein, insisting that his name be pronounced "Fronkensteen" and that he is not a madman but, rather, a scientist. He then lectures 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, who is the grandson of Victor's henchman. Igor tries to convince him to continue in his grandfather's footsteps ("Together Again for the First Time"). He reveals that he has already hired the services of Inga, a yodeling lab assistant with a degree in Laboratory Science from the local community college.

The three join together and hop on a wagon. During the ride to the Castle Frankenstein, the doctor becomes more familiar with Inga ("Roll in the Hay"). When they reach the castle, they meet the very mysterious Frau Blucher. Once inside the castle's main room, Frederick falls asleep while reading Rebecca of Sunnybrook Farm and dreams that his grandfather and ancestors tell him to build a monster ("Join the Family Business"). He is awakened by Inga and, after some unique exploring, they find the secret entrance to his grandfather's laboratory by following the sounds of eerie violin music.

They discover that the mysterious violin player is Frau Blucher, who tells of her past of festival games 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. They dig up a huge corpse with "an enormous schwanstuker." The villagers, meanwhile, gather at the local town hall for a meeting and are instructed to be on the lookout for grave robbers ("The Law").

Frederick sends Igor to find a brain and entrusts him with the vital organ, but the henchman drops it, surreptitiously replacing the brain with another. Upon Igor's return, Frederick carries out the experiment and brings the creature to life ("Life, Life"), who goes on an unexpected rampage shortly after waking. The doctor is distressed to find that Igor had provided a different brain.

Inspector Kemp and the townspeople come to investigate, pretending to welcome Frederick ("Welcome to Transylvania"). Frederick and his employees, however, try everything possible to stall the villagers as Frau Blucher frees the Monster without letting Frederick know ("Transylvania Mania"). Panic ensues as the monster breaks free from the stage and tramples through the house just as the curtain falls.

Act Two

Everyone is out to search for the Monster. Even Frau Blucher tries bringing back the Monster with the music from the violin, but to no avail ("He's Loose"). The doctor, who is visibly frustrated, is approached by Inga. She attempts to encourage the doctor and instill faith in him again ("Listen to Your Heart"). Elizabeth arrives unexpectedly in Transylvania with a large entourage and finds Frederick and a naked Inga, who insist that there was no funny business taking place ("Surprise").

Elsewhere, the Monster finds a blind hermit named Harold after breaking through his house wall ("Please Send Me Someone"). After Harold accidentally pours hot soup into the Monster's lap and lights his thumb on fire, the Monster is startled into another massive 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 good looking fellow who is loved and will be hailed by all ("Man about Town"). He has won the Monster over.

The Monster is then presented at the Loews Transylvania Theatre, now dressed as a dapperly gentleman. He is walking on command and even dancing with some grace to Irving Berlin's "Puttin' on the Ritz." While taking his bow, the Monster becomes terrified when a couple of stage lights explode. In the chaos, Elizabeth is kidnapped by the creature, taken to a cave.

However, she sees a different side of the Monster ("Ah! Sweet Mystery of Life"). Quickly forgiving him, she connects with the creature and discovers what she has been yearning in 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 that he is able to bring him back to life. Just as the crowd is about to rehang Frederick and the Monster, Elizabeth arrives. After a hopeful plot twist, the Monster proposes to Elizabeth ("Deep Love – Reprise"). Then, the blind Hermit's voice is heard singing; Frau Blucher announces she has a "blind date" with him. Igor proceeds to proclaim a false miracle, saying that his hump is gone... but then quickly realizes that it has just moved. Inspector Kemp and the villagers all elect the Monster as Mayor of the Town, which he gladly accepts.

Suddenly, Count Dracula appears, wishing to purchase the castle on the hill, but Frederick tells him that the castle is not for sale, that he will be living in it and continuing the family business from now on. He then proposes marriage to Inga, which she gladly accepts. All in all, our characters are happily together and the town celebrates. It is a happy ending that is sure to bring laughter and love for all ("Finale Ultimo").