Kids on Greenwillow Lane learn about trash, treasures, and trading, with Megan Whitney learning the most important lesson of all. A "block yard sale" is fun for kids, as well as a learning experience, and when a baby is for sale, it adds to the excitement. While the other children on this cul-de-sac discover one another's treasures, Megan tries to sell her little brother. Max wants to buy him, but his brother Alex says their mom doesn't want any more kids. Meanwhile, the baby disappears. It seems Jon has been sold, or kidnapped. Will Megan try to get him back?