A grisly murder at a convent baffles Medical Examiner Maura Isles and Det. Jane Rizzoli at the start of this assured, richly shaded seventh novel from bestseller Gerritsen (The Apprentice; The Surgeon,
etc.). The popular duo are called to Boston's Graystones Abbey when two nuns are discovered in an abandoned chapel, one dead and the other near death, both brutally bludgeoned. Red herrings are everywhere: Isles's discovery that one of the murdered nuns had recently given birth (followed shortly by the discovery of the baby's body in a pond near the convent); the murder of a homeless derelict with her face and extremities removed by her killer; and the lurking menace of a multinational chemical company. Complicating matters further is the sudden arrival of Isles's ex-husband, Victor, a celebrity humanitarian with his own suspicious connection to the case, and Rizzoli's old flame, FBI agent Gabriel Dean, who's responsible for the baby now growing in Rizzoli's belly. The investigation is rather low-key, but Gerritsen gives atmospheric depth to her tale with descriptions of snowbound Boston and an exotic past tragedy. Isles's pleasantly bitchy coldness ("Go ahead and pass me, idiots. I've met too many drivers like you on my slab") gives a welcome edge to the proceedings, and the struggles of both Isles and Rizzoli to balance their tough professional acts with romantic drama are satisfyingly gritty. BOMC main selection; 6-city author tour. (Aug. 19)