1903. Sherlock Holmes and Dr John Watson have tickets to the newly arrived Circus of Amun-Ra. Holmes is puzzled by his brother Mycroft's cryptic gift but is intrigued enough to attend the next production.

The performers, dressed as wondrous half-animal, half-human gods from Egyptian mythology, display superhuman agility and stunts. But they speak no Arabic, sequester themselves in the stables after each show and take orders from a mysterious ring master who is yet to be seen. And then one of the performers is murdered.

Holmes's enquires lead him to a townhouse near Gorsvenor Square, the home of the beautiful and secretive socialite Dorian Gray. As Holmes digs deeper, he learns Gray is hiding much more than his involvement in a murder in a darkly fantastical tale of lies, experimentation, hypnosis and wicked ambition.