When Dawn starts getting threatening notes and add phone calls while she's babysitting, she doesn't know what to do. The notes are signed "Mr. X," and they're beginning to get scary. Normally, she would tell the other Baby-sitters, but this time is different.

Kristy is determined to find Jake, a member of her softball team who has been missing for over two days.

Mary Anne discovers a secret about her past and now she's afraid of the future.

Claudia's room has been ransacked, and her sister Janine is acting strange. It's up to the Baby-sitters to solve the mystery.

Claudia and the rest of the Baby-Sitters Club decide to investigate at the new museum when someone steals some priceless coins and one of the sculptures appears to be a fake.

With the help of her friends in the Baby-sitters Club, Dawn is able to find out what happened to several dogs that have mysteriously disappeared.

Jessi can't wait to get to New York City to see her friend Quint dance in his first big ballet.

Who would have believed it? Counterfeit money is showing up in Stoneybrook.

A new passion for photography has Claudia snapping pictures everywhere she goes, including the Stoneybrook Bank, and when it is discovered that a robbery took place at the bank on the very same day, Claudia thinks her photos may contain evidence.

Someone is setting small fires in the Stoneybrook library and Mary Anne is determined to find the culprit.