Boston PIs Patrick Kenzie and Angela Gennaro have been hired to find a six-year-old girl who vanished from her home without a trace. Despite enormous public attention, extensive news coverage, and dogged police work, the investigation has gone nowhere. But it's a case rife with sinister circumstances: a strangely indifferent mother, a pedophile couple, a bizarre subculture of homeless parents, and a shadowy police unit with a covert agenda and no qualms about enforcing it.