Freddy and his best friend Cara babysit for a little boy named Tyler and terrorize him with stories about werewolves. Right in the middle of one, the door flies open and they all get freaked until they realize it's just his parents. They walk home, and Freddy walks Cara to her house before heading back to his.
Cara comes over the next day and they hang out in his basement playing air hockey. Things get a little rough, she starts chasing him around, and he crashes into a china cabinet. After it falls and breaks, they find a doorway that they never noticed before. Freddy and Cara both find flashlights and venture into the long tunnel behind the door.
It leads them underground and into a room that is empty except for a coffin. Cara gets a little scared, especially when Freddy decides to open it. The only thing inside is a bottle with a label on the front that says Vampire Breath. They fight over it, and Freddy gets scared when Cara opens it. A weird mist fills the room before he can put the lid back on the bottle, and they suddenly see an old man inside the coffin.
The man wakes up, says his name is Count Nightwing, and he admits that he is a vampire. The Count chases them around until they run down the tunnel, and the door closes before they can escape. The Count tries to bite Cara, but realizes that he lost his fangs. The only way he can remember where he put them is by using the Vampire Breath.
He also decides that he won't kill them if they help him find the bottle. He claims that he was asleep for more than 100 years, and the bottle will let him go back to his own time. They track down the bottle and he opens it, but they end up going back in time with him. The Count still wants to eat them and whines about being hungry so they run off.
Cara wants to leave the castle they're in and look for help outside. They climb out of a window and almost die when they discover that they're now on the side of a cliff. The Count finds them and saves them but they run away again. They find a little girl named Gwendolyn who is around their age. She tells them that she's a slave who has to clean the coffins of the vampires, and she shows them multiple rooms filled with coffins.
She offers to help them escape and takes them into a hidden room, only to reveal that she's a vampire. Just as she starts to bite Freddy, the Count shows up again. They discover a room filled with empty bottles of Vampire Breath, and the Count thinks that one is the bottle that he hid away. He grabs one and opens it, but it's an empty bottle.
Freddy manages to find and open a filled bottle, and it sends them back to their time, but the Count comes with them. Just as he starts rambling again, Freddy's parents walk into the basement, and his mom greets the man, calling him daddy. She says that he has been sleeping for more than 100 years down there and it was about time he woke up from his nap.
Freddy's mom also tells her dad that his fangs are in a cup in the bathroom, the same place he left them when he “laid down for a nap.” Freddy asks if that makes him a vampire too, and she tells him that he is, but he's too young for fangs because those won't come in for 100 years. All three turn into bats and fly away. Cara makes a joke about how she always knew he was weird, and they decide to check out the bathroom. She finds a vial of Werewolf Sweat, and even though he begs her to leave it alone, she opens it. Freddy asks her a question, and the book ends with her growling in response.
*Tyler's parents are pretty crappy parents. They know that Freddy keeps telling their son scary stories, and he has trouble sleeping because he's so scared, but they don't say anything until after they get home at the end of the night.
*Yeah, and Freddy and Cara walk home because they live close by. Um, no. It's late at night and they are basically tweens, so someone should walk/take them home.
*If you kept your vampire father hidden in the basement, would you really turn that space into a game room with a pool table, air hockey, table, etc. where your son plays with his friends?