Do not open! It sucks!

THE THIRD BOOK IN THE DO NOT OPEN! SERIES |

Nemo has had enough! Especially right now, when he has to study for a maths test! He really doesn't have time for another monster! When he finds another package at his door, he doesn't even open it and takes it straight back to the post office. Good idea, he and his friends think.
But then unbelievable things start to happen in the town. Upper Oddbodge is suddenly plunged into pitch-black darkness. And that's not all.
Someone must have opened the package! And whatever was inside is now running around town! Nemo, Oda and Fred have no idea what it is. All they know is that someone scribbled on the package: “Do not open! It sucks!”
Everyone is terrified. What now?