20 - Survivor In Death (In Death #20) by J.D. Robb

Murder was always an insult. But the murder, bloody and brutal, of an entire family in their own home, was a different form of evil.

Nixie Swisher crept down the stairs for a drink - and saved her own life.
When Lieutenant Eve Dallas is called to the house minutes later, she finds the whole family murdered in their beds. But the killers made a mistake: they left a survivor.

Nixie saw everything. And unfortunately for her, these elite killers soon realise they need to finish the job.

ID - 20