With thrills, chills, and laughs on every page, this gruesomely funny book will leave you seeing double! In this third book in the acclaimed middle grade series. Three monster-obsessed friends accidentally unleash an army of evil twins onto their hometown. Nick, Carter, and Angelo have defeated the Zombie King, taken down a mad scientist, and, toughest of all, even learned to cooperate with their monster-loving girl rivals. But when the three friends head on a camping trip with Nick's parents, a fateful hike in the woods leads the boys to a creature that can change its shape at will and even mimic the boys' voices. Carter sneaks the little guy into his backpack and takes him home, and so the trouble begins. And in this frighteningly funny adventure, trouble always comes in twos. . . .