Gone, Baby, Gone: Dennis Lehane

Boston private investigators Patrick Kenzie and Angela Gennaro are hired to find four-year-old Amanda Cready.
Despite extensive news coverage and dogged investigation into her abduction, the police have uncovered nothing. And as the Indian summer fades, Amanda McCready stays gone - vanished so completely that she seems never to have existed.
Then a second child disappears.
Confronted with a police force seething with lethal secrets, Kenzie and Gennaro soon discover that those who go looking for the missing may not come back alive.