Will has never been to the outside, at least not since he can remember. And he has certainly never got to know anyone other than his mother, a fiercely loving yet wildly eccentric agoraphobe who drowns in panic at the thought of opening the front door. Soon the confines of Will's world close in on him. Despite his mother's protests, he ventures outside, clad in a protective helmet, and braces himself for danger. He eventually meets and befriends Jonah, a quiet boy who introduces him to skateboarding, and finds his fears fading and his body hardening with each new bump, scrape and fall. But life quickly gets complicated when a local boy goes missing, and Will and Jonah embark upon an extraordinary adventure ...