DISAPPEARANCE AT DEVIL's ROCK by Paul Trembly

Tommy Sanderson is on summer vacation. He is hanging with friends just like most other kids his age.  A new guy in town is welcomed into this group. But Arnold is much older.  Exactly how old, the boys don't know.  The parents are unaware of Arnold until Tommy doesn't come home and the police question the boys.  Josh and Luis, Tommy' best friends, and Tommy snuck out in the middle of the night.  Three boys went out but only two came back.  Where is Tommy and what is happening to him?  Do his mother, Elizabeth, and his sister, Kate, see him or maybe his ghost in the house?  Who is dropping pages from Tommy's journal on the floor?  A must read mystery.