In 1915, Sherlock Holmes is retired and quietly engaged in the study of honeybees in Sussex when a young woman literally stumbles onto him on the Sussex Downs. Fifteen years old, gawky, egotistical, and recently orphaned, the young Mary Russell displays an intellect to impress even Sherlock Holmes. Under his reluctant tutelage, this very modern, twentieth-century woman proves a deft protégée and a fitting partner for the Victorian detective.

Detective Lauren Pengelly has only been part of the Penzance police force for less than two years, but that’s enough time to know that the sleepy Cornish town doesn’t see many murders. So, when the bones of a woman with a hole in her skull are discovered behind a derelict cottage, she immediately assumes the worst. Rallying her team, Lauren is flooded with a strange sense of relief when the bones turn out to be almost twenty years old, not a recent victim. But it quickly turns to dread when she receives her second heart-stopping call of the day–a little girl, Isla, has been kidnapped.

It's 1811, and the threat of revolution haunts the upper classes of King George III's England. Then a beautiful young woman is found savagely murdered on the altar steps of an ancient church near Westminster Abbey. A dueling pistol found at the scene and the damning testimony of a witness both point to one man - Sebastian St. Cyr, Viscount Devlin, a brilliant young nobleman shattered by his experience in the Napoleonic Wars.

London, 1962: The world is teetering on the brink of nuclear war but life must go on. Celia Duchesne longs for a career, but with no means or qualifications, passes her time working at a dusty bookshop. The day a handsome American enters the shop, she thinks she might have found her way out of the monotony. Just as the excitement of a budding relationship engulfs her, a devastating secret draws her into the murky world of espionage.

Northern Ireland, spring 1981. Hunger strikes, riots, power cuts, a homophobic serial killer with a penchant for opera, and a young woman’s suicide that may yet turn out to be murder: on the surface, the events are unconnected, but then things—and people—aren’t always what they seem. Detective Sergeant Duffy is the man tasked with trying to get to the bottom of it all. It’s no easy job—especially when it turns out that one of the victims was involved in the IRA but was last seen discussing business with someone from the loyalist Ulster Volunteer Force.