The Hollow by Michael Connelly

When retired LAPD detective Harry Bosch joins a lawsuit against the county for the running of the MacLaren Children's Center, it brings back memories of his time living there in the 1960s and his friendship with a boy named Charlie "Chops" Lamb. Chops was murdered in 1965 at the center, but no one was ever charged. Harry decides he wants to find out who was responsible for the crime and begins investigating. Harry's looking into the case unearths the name of someone Harry thinks might be responsible. It also puts Harry onto an ongoing case, working with the FBI, since this person seems to be a career criminal. In The Hollow, Connelly explores Bosch's childhood through the lens of a character that readers have known for over thirty years.