This is book number 8 in the William Monk series.
Deep in London’s dangerous slums, Victorians transact their most secret and shameful business. For a price, a man can procure whatever he wants. But for one such man, the price he pays is his life. In sunless Water Lane, respected solicitor Leighton Duff lies dead, kicked and beaten to death. Beside him is the barely living body of his son, Rhys. The police cannot fathom these brutal assaults until shrewd investigator William Monk, aided by nurse-turned-sleuth Hester Latterly, uncovers a connection between them and a series of rapes and beatings of local prostitutes. But then the case takes an even more shocking turn.