When the Aldens spend the summer riding on a train, they get to live in a train car once again - this time, they're staying in Caboose No. 777. The number is hard to forget, and indeed, the children meet people at each stop who seem to know it well. It turns out Caboose No. 777 has an unusual past - one that comes with its very own mystery!

A young Canadian visitor helps the Alden family solve a mystery involving a lost coin collection.

The Aldens climb a mountain and find a mystery! The hike up Old Flat Top was only supposed to take a day, but a dangerous rockslide changes everything to reveal a hidden cave that just may hold a legendary treasure!

A hard-bitten former search-and-rescue dog helps solve a complicated missing chicken case.

When Kristy, Claudia, Mary Anne, and Stacey, the members of the Baby-sitters Club, each receive mysterious calls while they are working, they decide to find out who is responsible.

When his best friend Gabe is reported missing, Ali Cross sets out to find him, but he soon learns that being a kid sleuth is not easy and clues are not always what they seem.

While trying to help a friend out of a difficulty, teenage detective Nancy Drew has a perilous experience in and around a deserted bungalow.

A family, snowbound in a vacation cabin, discovers adventure in surrounding wild life, three children they find in the snow, and a search for a lost recipe.

While searching for the guard end of a broken saber that will solve one mystery, the Hardy brothers become involved with a gang of bank robbers.

Thea Stilton returns to her old school, Mouseford Academy, to teach a course in adventure journalism, and investigates a mystery involving a strange inscription and a missing person along with five female students.