William is very nervous about his first day at a new school until he meets a strange boy called Wrickety Stick. Wrickety - along with the rest of the Stick family - has bendable bones. He can make his bones go soft and thin just by concentrating. This means that he can do things that William can only imagine, like sliding under doors and squeezing into cracks, or slipping between the bars of a grate. After witnessing it for himself, William becomes fascinated and wants to know more about this strange family and their unusual bones.
But it's not just William who is interested in the Sticks' bones. The Sticks soon find out they are in danger - and William intends to help them. Though he can't slide under doors, he'll do everything he can to save his new friends.