Showing The Last Detective by Robert Crais

Elvis Cole's girlfriend, Lucy, is out of town, and she has left her young son, Ben, in Elvis's care. Elvis and Lucy have had a few problems lately - not least over his job as a private investigator. But at last things seem to be getting better.

Then Ben disappears. One minute he's playing his computer game in
Elvis's house; the next he has vanished. Elvis looks everywhere, but he
just can't find Ben; and neither can Lucy when she arrives.

Then Elvis receives a phone call about Ben - and realises that something
from his own past has come back to haunt him...