When their favorite pizza restaurant almost goes out of business, the Alden children try to help their friends stay open while they find out who is behind all their problems.

While on a cruise with their grandfather, the Alden children help discover who is behind the mysterious troubles of the ship--disconnected phone lines, engine trouble, a man overboard--and still have fun sightseeing, eating, and swimming.

Jessie and Henry's robotics team is competing in a big tournament. But when their robot is stolen, the Aldens have a high-tech mystery to decode!

When the Alden children spend a week visiting at Pilgrim Village, they uncover the mystery behind the unusual happenings at the historic site.

A mysterious woman, a dog barking every night at midnight, a puzzling note in the sand all add to a mysterious summer in a lighthouse.

The Aldens have joined Dr. Iris Perez as she investigates legendary creatures around the world. In this adventure, the children investigate what might be living in the deep trench off the coast of Puerto Rico. From manatees to mermaids to sea monsters, creatures of the sea have been attracting tourists to the area for years. But when a man on a nearby island goes missing, it's up to the Aldens to sort out fact from fiction.