There is a little boy who is afraid to go to sleep because of all the monsters, ghosts and other scary things he sees. When he talks about it with his mother, it turns out that he doesn't have to be afraid because his mummy will protect him against all the bad things.
Almost every child has a vivid imagination and each parent has to deal with monsters and ghosts at one time or another. Mom! The Monsters! shows in a playful way that there is nothing to be afraid of. Mummy (or daddy) will chase or send them away, so that everyone can go to bed safely.
