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. A parents' guide explains how well-intentioned adults often encourage children, especially young boys, to ignore and "put away" their feelings instead of learning to fully live with them. This simple but powerful story not only teaches children how to "control" their emotions but discourages suppressing them, the illustrations becoming more colorful and vibrant as Max moves out from his box's shadow.