Detective Simon Ziele lost his fianceé in the wreck of the General Slocum and shortly thereafter headed to Westchester County to escape the violence of the city. But just a few months into his tenure, he catches the worst homicide of his career: a young woman is brutally murdered in her own bedroom in the middle of a winter afternoon. A day's investigating leads him to Columbia University's noted criminologist, Alistair Sinclair, and one of his subjects, Michael Fromley, who has a history of violent behavior and brutal fantasies. But what would lead him to target Sarah Wingate, a notable mathematics grad student at Columbia? Is it really Michael behind the murder, or is someone else copying his signatures? This is what Simon Ziele must discover, with the help of the brilliant but self-interested Alistair Sinclair, before the killer strikes again.