Oxana's sister, Olga, is coming over to visit, and much to Vampirina's delight she is bringing her new baby cousin, Nosferatu. Oxana plans to go out for some moonbathing with Olga once she arrives, and hopes that Boris will babysit little Nosy. However, he was planning to watch his favourite monster football team, the Transylvania Trolls, play against the Frankenberg Spooks. So, Vampirina volunteers to babysit Nosy so her dad can watch the game. She always wanted to be a babysitter and a big sister. Oxana grants her permission to babysit Nosy, as long as Gregoria and Demi help. Though Demi is excited about babysitting, Gregoria is not so keen on the idea, saying that vampire babies are a great deal of trouble.
Vampirina invites Poppy and Bridget to help out as well. Poppy brings along some human baby toys for Nosy to play with, though both Vampirina and Demi state that baby vampires are different than regular human babies. At last, Vampirina's Aunt Olga arrives with her baby cousin. She leaves Nosy in Vampirina's care, and both Olga and Oxana fly off for some moonbathing while Boris heads off to watch the game. So far, all is going well with babysitting Nosy. However, as they play a game of peekaboo, Nosy starts running around at super vampire speed. Vampirina and her friends try to catch her, but she is too fast for them, especially for Vampirina. Nosy crawls onto the piano. Poppy tries to distract her by getting her to play with a xylophone. Suddenly Nosy lifts up the whole piano, and spins it on her finger. She does not put the piano down until Vampirina convinces her to come up for a hug. Relieved, Vampirina and her friends finally have Nosy under control. She did not expect that babysitting a baby vampire would be so difficult, but was determined to keep her promise to her mom and aunt. Poppy offers Nosy some more human baby stuff, like a teddy hat and a bouncy ball. Nosy flips the hat off her head and bites through the ball with her baby fang. Vampirina decides to take Nosy to the kicthen and give her some dinner. She serves up a cauldron of scary-berries with milk. She tries to hand feed Nosy, but she suddenly grabs the cauldron and drinks from it. Then she gets the battys and spills scary-berries and milk everywhere. Poppy suggests feeding Nosy with a baby bottle, but Vampirina again states that baby vampires only eat from cauldrons and not bottles. Just then, Vampirina hears her dad coming, and quickly clears up the mess.
Boris arrives in the kitchen to get a snack, and also checks on Nosy, who looks all innocent to him. After he leaves, Vampirina and her friends decide it is time for Nosy's nap, but discover that she has disappeared again. To make matters worse, they discover that Wolfie has had some of the milk Nosy spilt on the floor, and turned into a werewolf. Demi and Gregoria search for Wolfie, while Vampirina, Poppy and Bridget look for Nosy. The girls find her in the living room, and chase after her up to Vampirina's bedroom. Nosy transforms into a bat and flies off outside. Vampirina flies after her. Meanwhile, Demi and Gregoria find Woflie in the backyard, and Nosy lands on his head. Vampirina starts to feel doubtful about her decision to babysit. Her mom and aunt were going to be back very soon. Poppy has one more idea, and despite it being a human baby thing Vampirina at this point will try anything. Together, Poppy, Vampirina, and Bridget sing to Nosy a lullaby, which puts both her and Wolfie to sleep.
They later put Nosy back in her pram, cuddled up with a pink teddy bear. Oxana and Olga also return from moonbathing. Olga thanks Vampirina and her friends for taking care of Nosy, and Vampirina thanks Poppy for all her help. She has comes to understand that vampire and human babies are not so different after all, just like her friendship with Poppy.
- Isabella Crovetti as Vampirina Hauntley
- Lauren Graham as Oxana Hauntley
- James Van Der Beek as Boris Hauntley
- Wanda Sykes as Gregoria
- Jordan Alexa Davis as Poppy Peepleson
- ViviAnn Yee as Bridget
- Mitchell Whitfield as Demi
- Dee Bradley Baker as Wolfie
- Kari Wahlgren as Olga/Nosferatu