In this book, Laura Gamerro and Manu Callejón present one of the most common childhood fears - the possibility that a monster is living in some hidden corner of the house - and the perfect way to conquer it: a manual of simple instructions with which the protagonists will trap their monster. Step by step, the children grow in courage and resolve as they cook, make traps, hide or prepare an ambush. As fear abates, so the monster appears and then all that remains is to see if they can make friends with him.