When the children uncover a strange puzzle in a friend's back yard, it's the start of a "spy game" leading to gold. But first they must make sense of an old photo and a riddle, and learn just who is behind this mystery within a mystery.

The Aldens are volunteering at the local recycling center, where they find plentyof things that can be reused, including a pinata that Benny takes home. But when the center is vandalized,the Boxcar children have a mystery to solve. is there treasure amidst the junk?

The Aldens are preparing for a yard sale when they find an old wooden mask in the trash behind a neighbor's house and discover it is an old Native American mask from the Hopi tribe. When the mask is stolen from their garage, the Aldens vow to find it before the weekend Pow-Wow. But with such little evidence, will they be able to find the mask in time? Illustrations.

The Aldens visit Grandfather's friend at the Ogopogo Retreat and aided by puzzling clues, embark on a treasure hunt to prevent the retreat from being sold.

The Alden children, isolated in a storm at a small bus station, are led into a mystery centering on a polluted river.

"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.

While helping out part time in a pet shop, the Alden children discover an employee who is smuggling and selling exotic animals.

When the Boxcar children help out in a local garden, they dig up one strange thing after another! First, the tomato plants seem to move every day. Find out how that can be.

A friendly writer with a metal detector, the mysterious inhabitants of a tower house, and the discovery of a locket in the sand are ingredients for the Aldens' latest mystery.