A bloodstained room, a missing woman, a passionate affair gone wrong. September in London, and the city basks in a glorious Indian summer. Sherlock Holmes has more work than he can handle, and when the Home Office asks him to sniff out a plot by Russian assassins on radical politician George Dashing, Holmes and Watson find themselves distracted by more pressing cases. Meanwhile, there is scandal at the home of Dashing's great political rival, Sir Henry Catanache. When Sir Henry's housemaid goes missing, leaving only a pool of blood behind, his son is the prime suspect. Can Sherlock discover the truth? Or will the Catanache family be rescued by Laurence Martin, a detective newly arrived in London who is dazzling society with some remarkable triumphs?