The Impossible Postal Express is no ordinary train. It's a troll-operated delivery service the runs everywhere -- from ocean-bottom shipwrecks to Trollville, to space. When this train comes roaring through her living room, eleven-year-old Suzy Smith's world turns upside down. She has no choice but to sneak on board and she suddenly finds herself deputy to the post master. She botches her first delivery to a cruel sorceress, by stealing a cursed snow globe containing a boy who claims there is a plot to take control of the Union of Impossible Places. Suzy has to make a difficult choice with the fate of the entire Union at stake.