Ceremony in Death, Nora Roberts

Conducting a top secret investigation into the death of a fellow police officer has Lieutenant Eve Dallas treading on dangerous ground. She must put professional ethics before personal loyalties. But when a dead body is placed outside her home, Eve takes the warning personally. With her husband, Roarke, watching her every move, Eve is drawn into the most dangerous case of her career. Every step she takes makes her question her own beliefs of right and wrong - and brings her closer to a confrontation with humanity's most seductive form of evil...