Gone, Baby, Gone

Description for GONE, BABY, GONE by Dennis Lehane:

The neighborhood is no place for the innocent, the young, the defenseless or the pure. This is a territory of broken families, bitter cops, whacked out ex-cons, and a mother who watches herself on the nightly news as her missing child floats further and further into the unknown. Boston private investigators, Patrick Kenzie and Angela Gennaro, don't want this case. But after pleas from the child's aunt, they embark upon an investigation and ultimately risk losing everything--their relationship, their sanity, and even their lives--to find this little-girl lost.

This is #4 in Patrick Kenzie and Angela Gennaro Series.