The Alden children discover another mystery when the agree to help injured Mr. Yee tend to his plot in the community garden and find out that vegetables are going missing and plots are being vandalized.

A local radio station is holding the Great Detective Race, and the Boxcar Children have entered the contest! They solve riddles and search all over town for clues leading to the grand prize. But when some of the clues turn out to be fake, it's clear that someone is playing unfairly! Who could be trying to ruin the race - and why?