Eleven-year-old Uma has always found safety in Barnaby, her threadbare teddy bear and "steadfast sentinel" against the dark. But the sanctuary of her bedroom is shattered when Barnaby begins to change. It starts with a "delicate, dry clicking" from his chest and a strange rigidity in his limbs. Then, Uma finds the first tooth: a tiny, white, "predatory" edge breaking through his stitched smile. As her "furry anchor" transforms into a "quiet threat," Uma must face a terrifying reality-her best friend is becoming a monster, and he's grinning right at her.