After losing his mother while solving a brutal murder, young Sherlock Holmes commits himself to fighting crime. While visiting his father at work, Sherlock watches a dangerous trapeze performance. When the troupe's star drops to his death, Sherlock notices something is amiss and realizes it was foul play.

Moira Moriarty, sister of James, works with Sherlock Holmes to solve the mystery of a string of family deaths, but they must deal with a mysterious photograph and secret safe houses to discover the truth behind James' secrets and betrayals.

In late nineteenth-century London, fourteen-year-old Enola Holmes, much younger sister of detective Sherlock Holmes, turns to Florence Nightingale for help when her investigation into the disappearance of a Crimean War widow grows cold.

While attending Baskerville Hall, a secret school for extraordinarily gifted children, Arthur Conan Doyle and his friends (and enemies) are invited into the Clover, an illustrious social club that requires them to pass three tests, an endeavor that leadsthem on a dangerous adventure.