On the death of his parents, a young boy is left in the care of his beloved grandmother. She knows things that others don't, and she is a fantastic storyteller. Through her stories, he learns one very important and scary fact: witches are real!

The Witches are not just fantastical creatures in Grandmamma's wonderful stories; they don’t wear black hats or have green faces or even ride broomsticks. They are demons disguised as friendly ladies and it is their number one purpose in life to get rid of children. Fortunately Grandmamma knows plenty about the vile creatures and the little boy learns how to spot them. Unfortunately the boy and Grandmamma end up in a hotel full of them, including the Grand High Witch herself.

Through a few spine-tingling, heart-stopping antics, the boy uncovers their sinister plan to kill all the children in England, and together with wise old Grandmamma he decides not to let them escape. With a little cunning and a lot of cleverness, they hatch a plan that will bring about the beginning of the end for all witches.