When Justin loses the special hat his grandmother made for him, he looks everywhere he can think of to find it. Everywhere, that is, except the lost and found. Mr. Rumkowsky, the old school custodian, is the keeper of all the lost and found items, and everyone is afraid of him, including Justin.
With his grandmother coming to visit soon, his mom upset, and the hat nowhere in sight, Justin finally musters the courage to enter Mr. Rumkowsky's domain. There he discovers a whole world of treasures - lost items Justin's friends (and generations of children before them) have been too afraid to claim. Things keep getting weirder and weirder, until way down at the bottom of Rumkowsky's giant box Justin unearths something completely unexpected...