The Aldens try to help a visiting Russian gymnast who is surrounded by mysterious people and events and who seems to have a secret.

While staying at an eighteenth-century inn in Vermont, the Boxcar children become curious about the mysterious "accidents" that keep plaguing the owners.

One warm night four children stood in front of a bakery. No one knew them. No one knew where they had come from. Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they're fixing up their boxcar so they can ride it in the big Greenfield Founder's Day parade. There's just one problem. Someone has stolen the boxcar with their dog, Watch, in it! If they can only find the missing boxcar, it...