After the deaths of her parents in a car accident, Heidi Davidson moves in with her uncle, Dr. Palmer Jekyll, in the town of Shepard Falls in Vermont. Soon after arriving, Heidi is warned by one of the locals that her uncle is responsible for a mysterious beast that attacks the town every night. While she initially laughs off the accusations, Heidi begins to discover that her uncle is indeed working on a mysterious project, and that the attacks on the town are real... but the cause is not what everyone thinks.
This book provides examples of:
- Covers Always Lie: While there is a scene where Heidi watches Jekyll drink a potion, he doesn't turn into a monster.
- Cruel Twist Ending: The ending reveals that Mariana bit Heidi in her sleep, meaning the curse has been passed on to her.
- Darker and Edgier: Much like most of Series 2000, but this time it's less about gore and more about moody atmosphere. The exception being a scene where a hamster is squeezed to death.
- Downer Beginning: The story starts with Heidi telling us about how she's moving to her uncle's house because her parents died in a car crash.
- Foreshadowing: At one point Heidi dreams about being bitten by a creature, and upon waking up, her shoulder feels sore. This hints at the twist that reveals Mariana bit Heidi in her sleep while in beast form.
- Gratuitous Laboratory Flasks: Heidi mentions seeing some the last time she visited Uncle Jekyll when she was 5.
- Nephewism: Heidi lives full time with her uncle now, after the death of her parents.
- Never Trust a Title: The title implies it will be a Jekyll/Hyde story when it really isn't. Even Mariana being the beast is more standard than the dual personality shtick of the original story.
- Not Using the "Z" Word: The story features a monster that most likely is a werewolf or at least something very similar to one, although this in not immediately obvious because the protagonist incorrectly thinks it is a different kind of monster for most of the book, but even after The Reveal of the monster's true nature makes it obvious that the monster is a werewolf, the word "werewolf" is never used in the book. Although Heidi does dream about being chased by a wolfman.
- Secret Diary: Heidi finds one that belongs to the beast, bemoaning their fate. It turns out to be Mariana's.
- Tragic Monster: It turns out the monster is Mariana, who was bit by a creature years ago. Since then, she has struggled with being a monster and Jekyll has been trying hard to fix it.
- Torches and Pitchforks: In the climax, the villagers all team up to attack Dr. Jekyll's castle, thinking he is the beast and wanting to kill him. They manage to burn his mansion down, but Jekyll and Mariana escape.