On a dark, rainy night, an elderly couple finds a shivering little boy on their doorstep who proclaims, "I was a rat." They take the boy in, but because of his odd rat-like behavior, people in the town declare the boy a monster. To save him, the couple must discover the truth of who he is, before it's too late. "I was a rat!" So insists a scruffy boy named Roger. Maybe it's true. But what is he now? A terrifying monster running wild in the sewers? The Daily Scourge newspaper is sure of it. A lucrative fairground freak? He is to Mr. Tapscrew. A championship wriggler and a budding thief? That's the hope of Billy and his gang. A victim of "Rodent Delusion"? So says the hospital doctor or just an ordinary small boy, though a little ratty in his habits? Only three people believe this version of the story. And it may take a royal intervention - and a bit of magic - to convince the rest of the world.