When their favorite author fails to arrive as scheduled to speak at the local library, the Alden children investigate how he could board a train and never be seen again.

The Aldens try to solve a series of mysteries which took place in a old hotel in Kansas which they visit.

While visiting an aquarium in Florida, the Aldens discover that the Ocean Adventure Park's great white shark has a very human enemy.

When the Aldens visit Yellowstone they discover a map showing the way to an old cabin where gold is supposedly hidden, but they encounter lots of interference in their attempts to hike the trail.

When the Aldens visit a university campus, they must solve a mystery involving an old library whose stone gargoyles seem to move on their own.

"Learning about paleontology and fossil hunting under renowned scientist Dr. Iris Prez while attending summer camp in Colorado, the Aldens investigate an outbreak of strange events that local superstition attributes to a bigfoot creature roaming the valley"--WorldCat.

While exploring the caves around Dragon's Mouth Cavern, a series of unusual and somewhat frightening events convinces the Alden children that someone does not want them around.

The Mystery of the Secret Message: The Aldens are helping their grandfather organize Greenfield's Winter Festival. When the Boxcar Children get a roll of photos developed, they find a secret message hidden in one of them. They are baffled, and things become even more mysterious when they realize that someone is trying to ruin the Winter Festival by tearing down the ecorations and stealing a local statue! There must be a connection between the message...

The Alden children stumble upon a mystery when they enter their dog, Watch, in a contest that could lead to fame and fortune, but where things keep going wrong.

"One day in the park, the Aldens' dog, Watch, comes across a mysterious box with a note inside. 'Congratulations!' the note says. 'You've found it!' The box is part of a game called Geocaching. Soon, Henry, Jessie, Violet, and Benny are searching all over town for hidden boxes and making friends with other kids in the geocaching club. But is one of the club members a thief?" -- p. [4] of cover.