On a fine summer's day in June 1914, Ian Rutledge is planning to propose to a woman he deeply loves, despite hints from his family and friends that she may not be the most suitable choice for a policeman's wife. To the north, another man in love—a Scottish Highlander named Hamish MacLeod—asks his own sweetheart to marry him.

Back in England, a son grieves for his mother, dredging up a dark injustice that will trigger a series of murders that Rutledge must solve. The victims are all upstanding and well-liked. The local police have their suspicions about the culprits and are less than cooperative with the London detective.

As clouds of war gather on the horizon, Rutledge digs deeper, finding similarities and patterns between the murders. With every moment at stake, he sets out to right a terrible wrong—an odyssey that will eventually force him to choose between the Yard and his country, between love and duty, and between honor and truth.