In her brilliant and terrifying new novel, Tess Gerritsen - bestselling author of The Surgeon and The Sinner - taps into the deep well of murder and obsession, and builds an almost tangible atmosphere of tension and suspense before arranging for an explosive release that is as horrifying as it is unexpected.

Dr Maura Isles makes her living dealing with death. As a pathologist in downtown Boston, she has seen more than her share of corpses. But never before has the lifeless body on the medical examiner's table been her own.

But there can be no denying the evidence: the dead woman before her and her close friend and colleague Detective Jane Rizzoli is the mirror image of Maura, down to the most intimate physical details. Even more chilling is the discovery that they share the same birth date and blood type. When a DNA test confirms that Maura's mysterious double is in fact her twin sister, an already bizarre murder investigation becomes a disturbing and dangerous excursion into a past full of dark and deadly secrets...