While staying at the Crooked House, the family home of their housekeeper Mrs. McGregor, the Aldens try to solve a riddle that will lead them to a hidden treasure.

A family starts out on a one-day mountain climbing excursion that becomes very exciting. In fact, it becomes an adventure for the former "boxcar" family. They unearth some mysteries and have a fine time in the process.

While in the Bahamas with Doc Ford, who is investigating invasive lionfish, Maribel, Luke, and Sabina find precious artifacts but outlaws learn of their find and come after them.

The Alden children agree to help their neighbor search for treasure she believes is hidden in her attic, but the quest becomes urgent when they realize that someone else is trying to find it first.

Casey's life in Langston has been charmed. She's the queen bee of her prep school, a shoo-in for prom queen, and on her way to the Ivy League come fall. She can't wait to leave the whole town of Langston behind her. That is until her father loses his job and she finds herself on the brink of losing her ticket out of town. The town of Langston is known for its picturesque lake and robust summer tourism. Everyone who lives in town has heard the rumors...

The Alden children travel on a Mississippi paddle-wheel steamer to visit an old family friend in his cabin near Hannibal, Missouri, and try to discover who is responsible for the mysterious activities near the house.

The Aldens accompany their grandfather to his class reunion and investigate the possibility of a buried Civil War treasure, and of a ghost in the bell tower, at Goldwin University.

A million dollars, or a clue? Police report a break-in at an elite hotel, and the suspects sound suspiciously like Amy and Dan. There's a car and speedboat chase and an angry mob! When there's a clue on the line, anything can happen.