Max's parents give him a very special gift: a tiny, magical box that will hold everything, from his toys to his feelings. Max learns, however, that feelings can't be put away as easily as toys. Each negative emotion he feels--anger, embarrassment, sadness, loneliness--gets added to the box, which grows and grows. Eventually it is so large that it keeps him from doing what he loves, like riding his bike and climbing trees. With some help from his friends and family, Max is able to turn the box into something beautiful and let it go.