Grandfather's friend, Mr. Yee, has broken his arm and can't tend to his beloved vegetable plot in the community garden. The Alden children gladly offer their services to help him with his prize-winning veggies. But they soon learn something mysterious is afoot at the community garden. Vegetables go missing, and it appears someone is intentionally vandalizing the garden plots. Luckily for the local community gardeners, the Boxcar Children are on the case