Summer 1889. Harrison Fearing Pell hoped for adventure when she signed on with the Society for Psychical Research as an occult investigator. Slogging through New York's sewers in pursuit of a "mud man" wasn't exactly what she had in mind. But the reeking monster terrorizing the dance halls of the Tenderloin leads her to an even more peculiar mystery - and the last man on earth Harry wishes to become entangled with.

James Moran is a prodigy in music, mathematics . . . and crime. Harry's older sister, the famed detective Myrtle Fearing Pell, has vowed to put him behind bars. But Harry owes Moran a personal debt, so when he demands her aid she can hardly refuse. It turns out that the brilliant black sheep of New York Society is part of a secret club at Columbia College whose members have started dying in bizarre ways that may not be accidents.

Thus begins one of the strangest cases of Harry's career, a tale of murder, cold-blooded revenge and fairytale bogeymen to make the Brothers Grimm shudder. As the bodies pile up, each preceded by sightings of the victim's doppelgänger, Harry and her stalwart friend John Weston must race against time to save a man who arguably deserves his macabre fate.