While staying at a hotel in New York City, the Aldens investigate a series of annoying pranks plaguing the management and guests.

The Aldens investigate when an old wooden mask they have found is stolen.

Henry, Jessie, Violet, and Benny have never been to a drive-in movie theater before, but they're visiting a friend who owns one. The children love to eat popcorn in the car and watch movies under the stars. But strange pranks are disrupting the fun. One night the sound system starts playing loud music during the movie, and a couple of the theater employees seem to be hiding a secret. Then, late at night, a ghost is seen walking around the empty grounds...

While on a camping trip with their grandfather, the Alden children try to find out about the loud music and missing food that threatens to scare away other campers.

While visiting a Navaho Indian reservation in New Mexico, the Aldens try to save a forest under threat of development by proving it is the site of a lost, buried village, but someone is sabotaging their dig.

When the Alden children accompany their grandfather on a trip to Seattle, they discover clues throughout the city, seemingly planted just for them.

The Aldens help out at a minor league stadium and investigate when it appears someone in the ballpark is stealing the home team pitcher's signals and relaying them to the batters of the other team.

The Alden's neighbor, Lina, thinks there's treasure hidden in her attic and she wants the Boxcar Children to help her find it. Of course, the children are eager to help search—but it appears they aren't the only ones looking for the treasure.

The Alden children plan to ride in their boxcar at the Greenfield Founders' Day Parade, but the newly refurbished boxcar is stolen a couple of days before the big event.

"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.