The year is 1909, and Artie Quick--an ambitious, unorthodox and inquisitive young Bostonian--wants to learn about crime. By day she holds down a job as a salesgirl in women's accessories at Filene's; by night she disguises herself as a man to pursue studies in Criminal Investigation at the YMCA's Evening Institute for Younger Men.

Eager to put theory into practice, Artie sets out in search of something to investigate. She's joined by her pal Theodore, an upper-crust young bachelor whose interest in Boston's occult counterculture has drawn him into the study of magic. Together, their journey into mystery begins on Boston Common--where the tramps and the groundskeepers swap rumors about unearthly screams and other unsettling anomalies--but soon Artie and Theodore uncover a series of violent abductions that take them on an adventure from the highest corridors of power to the depths of an abandoned mass transit tunnel, its excavation suspiciously never completed.

Will Theodore ever manage to pull off a successful spell? Is Artie really wearing that men's suit just for disguise or is there something more to it? And what chance do two mixed-up young people stand up against the greatest horror Boston has ever known, an ancient, deranged evil that feeds on society's most vulnerable?