Crusader's Cross by James Lee Burke

For detective Dave Robicheaux, memories -- including those of a strange and violent summer from his youth -- are best left alone. But a dying man's confession forces Robicheaux to resurrect a decades-old mystery with a missing woman at its heart. Her name may or may not have been Ida Durbin, and Robicheaux's half brother, Jimmie, paid a brutal price for entering her world. Now the truth will plunge Robicheaux into the manipulations of New Orleans' wealthiest family, into a complex love affair of his own, and into hot pursuit of a killer expanding his territory beyond the Big Easy at a frightening pace.