Descriere Hello, Monster!

Parents always tell their children to go play with other children on the playground. When the mother in Hello, Monster! tells her son to join another boy in the sandbox while he is happily playing by himself, he rebels. His mother never talks to strangers, and what if the other boy is a monster disguised as a child that will trap him in his underground kingdom with all the other children who cook his meals and look after his pet moles?