Detective Chief Superintendent St John (pronounced Sinjun) Harcourt has been seconded from New Scotland Yard to the police force in St Albans, an old market town 20 miles north of London, to investigate the murder of a nursing assistant who has been caring for a young, autistic boy in the local hospital.

With his team of Detective Sergeant Siobhan Burrows, also from New Scotland Yard, and Detective Constable Amy Rhodes, an up and coming young officer from St Albans, St John makes frustratingly little progress in his enquiries, except to discover that the murdered woman was pregnant.

Then,...