Ian Rutledge returns to his career at Scotland Yard after years fighting in the First World War. Unknown to his colleagues he is still suffering from shell shock, and is burdened with the guilt of having had executed a young soldier on the battlefield for refusing to fight. A jealous colleague has learned of his secret and has managed to have Rutledge assigned to a difficult case which could spell disaster for Rutledge whatever the outcome. A retired officer has been murdered, and Rutledge goes to investigate.

The daughter of a distinguished soldier, Bess Crawford follows in his patriotic footsteps, volunteering to serve her country as a nurse during the Great War. In 1916 she promises Lieutenant Arthur Graham that she will carry his dying request to a brother. When Bess arrives at the Graham house in Kent, Jonathan Graham listens to his brother's last wishes with surprising indifference.

Detective Sergeant Chris Waters got the call at 05.29 that July morning. This is it, said DCI Reeve, you'll be first there, it's all yours, you're the crime scene manager. Suddenly, after months of waiting and wondering, Waters finds himself in at the deep end, and alone at the scene of a puzzling murder. As the investigation proceeds, the detectives at Kings Lake Central find themselves visiting familiar places and talking to some familiar faces, while old enmities reappear in the incident room. Before this is over, Chris Waters will need to make a career-changing decision.

The story opens with the apparently accidental drowning of a sixth form student in the Norfolk countryside. As a matter of routine, or so it seems, the case passes across the desk of Detective Sergeant Smith, recently returned to work after an internal investigation into another case that has led to tensions between officers at Kings Lake police headquarters. As an ex-DCI, Smith could have retired by now, and it is clear that some of his superiors wish that he would do so.

In a peaceful retirement village, four unlikely friends meet weekly in the Jigsaw Room to discuss unsolved crimes; together, they call themselves the Thursday Murder Club. When a local developer is found dead with a mysterious photograph left next to the body, the Thursday Murder Club suddenly find themselves in the middle of their first live case.