The Latin phrase is scrawled in blood at the scene of a young woman's brutal murder：I HAVE SINNED. It's a chilling Christmas greeting for Boston medical examiner Maura Isles and Detective Jane Rizzoli, who swiftly link the victim to the sinister Mephisto Club, a cult of scholars who aim to prove that Satan himself exists among us. Then, with the grisly appearance of another corpse, it's clear that someone-or something-is indeed prowling the city. Soon the members of the club begin to fear the very subject of their study. Could the maniacal killer be one of their own-or have they inadvertently summoned an entity from the darkness? Delving deep into the most baffling case of their careers, Maura and Jane embark on a terrifying journey to the very heart of evil.

Tess Gerritsen is a physician and an internationally bestselling author. She gained nationwide acclaim for her first novel of medical suspense, the New York Times bestseller Harvest. She is also the author of the bestsellers The Surgeon, The Apprentice, The Sinner, Body Double, Vanish, Life Support, Bloodstream, and Gravity. Tess Gerritsen lives in Maine. Visit her website at www.tessgerritsen.com.From the Hardcover edition.