Forensic archaeologist Ruth Galloway has excavated a body from the grounds of Norwich Castle, a forbidding edifice that was once a prison.

She believes the body may be that of infamous Victorian murderess Jemima Green. Called Mother Hook for her claw-like hand, Jemima was hanged in 1867 for the murder of five children in her care.

DCI Harry Nelson has no time for long-dead killers. Immersed in the case of three infants found dead, one after the other, in their King's Lynn home, he's convinced that a family member is responsible, though others on his team think differently.

Then a child goes missing. Could the abduction be linked to the long-dead Mother Hook? Ruth is pulled into the case, and back towards Nelson.