Among the "Ghosts". Book 1. Haddix M.P.

Luke 12 years old, and he never went to school, did not celebrate birthdays, and almost does not know how to read. Unlike two older brothers. He lives in the attic secret from everyone, and the brothers can play with friends and walk where he wants. He never risked appearing in open spaces, even if there was not a soul there. What's wrong? Why do parents look back when he wants to just push the curtains and look at the road?