Eleven-year-old Suzy Smith knows exactly how the world works. That's science, and Suzy's good at science. But when she wakes in the middle of the night to find a troll building train tracks through her living room, defying all the laws of space and physics, Suzy's world is turned upside down. How is any of this possible? As the trolls explain, it's "fuzzics," which is like physics only fuzzier! Well Suzy has no choice but to sneak on board and wrangle herself a position on the Impossible Postal service, a train that delivers to impossible places-everywhere from ocean-bottom shipwrecks to Trollville to space! Then, on Suzy's very first delivery-to the evil Lady Crepuscula of the Obsidian tower-the package itself begs not to be delivered. A talking snow globe claiming to be a prince, Frederick promises that the fate of the entire Union of Impossible Places now rests on Suzy's shoulders. But protecting Frederick may mean lying to and even endangering her friend and colleague, the postmaster Wilmot. Can Suzy save her friends and the entire Union of Impossible Places-all while upholding her duties as deputy postmaster?