Summer vacation on an almost private island gives the Aldens a challenge.

The Aldens visit their mysterious Aunt Jane at her run-down ranch and make a surprising discovery.

The Aldens are excited to visit a deserted South Seas island. But soon they discover clues that they are not alone. Is someone watching them?

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!

Because they do not want to be separated, four orphaned children run away and live in an old abandoned boxcar

The Alden children are visiting Aunt Jane when a nearby house burns down. Their friend Mike is blamed for starting the fire. Can the Aldens help find the real criminal?

"When the Alden children see odd lights coming from a closed amusement park and they receive a phone call warning them to stay away, they are determined to figure out what is going on at the park"--

"The Alden children love helping out at a local pizza parlor, but a blackout and other problems make them wonder if someone is trying to shut down the business"--