Spencer and his little sister, Katherine, are flying to Pennsylvania for Christmas with their dad. While changing planes, a blizzard moves in and cancels all flights out of Hoover Airport: they must stay in a basement room with the other unaccompanied minors. Spencer and four others - a chubby boy, a non-stop-talker, a surly girl, and a rich kid - go AWOL and get in trouble with Mr. Porter, the Christmas-hating airport supervisor. The five misfits spend the night evading and enduring Porter's punishments, discovering all sorts of things in back rooms, making sure Katherine gets her visit from Santa, and finding among themselves a new kind of family.