London's Second City has been the scene of many a terrifying crime, but the discovery of a pile of infant skulls unearthed near police headquarters is particularly horrifying. Although most of them are prehistoric, there is one that is certainly a lot more recent. But for John Coffin, Chief commander, there is another, more pressing, matter: the inexplicable triple murder of a midwife and her two daughters. The obvious suspect is her son, Black Jack Jackson, a local villain, but both Coffin and DI Phoebe Astley are reluctant to accept his guilt.
A further murder seems, in a macabre fashion, to connect the two investigations. But when other apparently random acts of violence occur, including a bizarre attack on a school bus and the death of a chief suspect, the picture gets increasingly confused. Is the mother-and-baby Walker club involved in some way? What of the provenance of the newer skull? For Coffin time is running out: the body count is rising and he needs to find a solution fast.