The Boxcar Children, now living with their grandfather, spend the summer on their Aunt Jane's ranch. Their aunt seems quite unhappy until at the end of the summer a surprise discovery brings happiness to all

The Alden children meet Mike Wood and a strange chain of events begins. Mike's house is mysteriously burned down, a man in a blue hat appears, and the Alden's uranium mine is in danger of being sabotaged. The four children solve the mystery.

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 visiting a recent purchase of Grandfather's, a ghost town in the Rocky Mountains, the Aldens encounter a mystery involving a run-down motel and a woman who may be a ghost