The beautifully ornate reading room at the Boston Public Library is completely silent one weekday morning, until a woman's terrified scream echoes through the room. Security guards immediately appear and instruct everyone inside to stay put until they determine there is no threat. While they wait for the all-clear, four strangers who had been sitting in the reading room get to chatting and quickly become friendly. Harriet, Marigold, Whit, and Caine each have their own reasons for being in the reading room that morning--and it just happens that one of them may turn out to be a murderer.