When a severed hand, clutching a gun, is found in a Chinatown alley in downtown Boston, detective Jane Rizzoli climbs to the adjacent rooftop and finds the hand's owner: a red-haired woman whose throat has been slashed so deeply the head is nearly decapitated. She's dressed all in black, and the only clues to her identity are a throwaway cell phone and a scrawled address of a long-shuttered restaurant.