When the Alden children go camping on Blizzard Mountain, a place said to be inhabited by a ghost looking for buried treasure, they begin to think someone or something is trying to scare them off.

When a professional hockey player comes to Greenfield with plans to build an ice skating rink, the Alden children suspect that someone in town wants to stop the project.

The Aldens, while testing the latest version of their favorite computer game, are surprised to find messages directed specifically at them.

The Boxcar children uncover a mystery on a train trip from Boston to San Francisco.

The four Alden children, aged six to fourteen, uncover a mystery while volunteering at a food pantry for the needy.

Someone or something is making a mysterious tapping sound at midnight in the home of a famous inventor known for her one-of-a-kind clocks. There is an invention convention taking place in the home and the Alden children are competitors at the convention. Does the mysterious tapping mean trouble for the convention? The children are determined to find out.

The Aldens take part in a hunt at a gem mine and discover that someone is out to sabotage the contest.

The Aldens become involved in a community theater production of "The Wizard of Oz," which is systematically and mysteriously being sabotaged.

When they help out at a guide dog training school, the Alden children meet several people who seem obsessed with a particular dog named Ginger.

While visiting the Florida Keys, the Aldens encounter suspicious characters, strange incidents at night, and a plot to steal valuable coral.