100 Cupboards by N.D. Wilson
Henry is not looking forward to reuniting with Aunt Dotty, Uncle Frank, and three girl cousins. Since his parents have been declared missing, he finds himself riding on a bus to Henry, Kansas.
Henry had taught himself at an early age never to look forward to anything.
Upon arriving in Kansas, Henry finds out that he is to stay in the attic room. On the very first night he woke up, was on his way to the bathroom when he saw a light under the door. Not wanting to disturb anyone he sat on the steps to wait. Out of the bathroom came a very old, bald man with a purple trailing robe. He continued on his way into Grandfather's room. This very same room has not been opened since Grandfather died 2 years ago. No one can get in.
On the second evening Henry closed his door, only to fall asleep with the lights on. Suddenly he jerked awake not really knowing why, when he felt a chunk of plaster rolling down his forehead.
He looked up to see more plaster coming and two knobs protruding from the plaster on the wall.
One of the knobs was turning ever so slightly...