During a heat wave in New York City, a literary agent is murdered in her Brooklyn apartment. Across the hall in 3B, aspiring writer Ruby Neptune finds herself sucked into the murder investigation of a neighbor she barely knew and didn't really like. The agent seems to have known her killer, as there was no forced entry. Ruby slowly discovers that many of her neighbor's friends had strong reasons to want her dead. Determined to find the killer, Ruby puts her own life on hold, which upsets her closest friends, one of whom suspect that her new boyfriend is capable of the murder. As the list of suspects narrows, it hits uncomfortably close to home and Ruby finds herself lying to friends and even putting aside her writing career to solve the case. But will Ruby be able to identify the killer before she becomes the next victim?