June 1815. The people of London wait, breathlessly, for news as Napoleon and the forces united against him hurtle toward their final reckoning at Waterloo. Among them is Sebastian St. Cyr, Viscount Devlin, frustrated to find himself sidelined while recovering from a dangerous wound he recently received in Paris. When the mutilated corpse of Major Miles Sedgewick surfaces from the murky waters of the Thames, Sebastian is drawn into the investigation of a murder that threatens one of his oldest and dearest friends, Irish surgeon Paul Gibson.