When an adolescent boy's mutilated body is found, it doesn't take long for the police to realize that this is the work of a serial killer.

Scotland Yard's new chief inspector Nicholas Drummond is on the first flight to New York when he learns his colleague, Elaine York, the "minder" of the Crown Jewels for the "Jewel of the Lion" exhibit at the Metropolitan Museum of Art, was found murdered. Then the centerpiece of the exhibit, the infamous Koh-i-Noor Diamond, is stolen from the Queen Mother's crown. Drummond, American-born but raised in the UK, is a dark, dangerous, fast-rising star...

"Impenetrable. Well protected. Secure. Home to the most valuable jewels on earth. But once a year, when the Queen attends the State Opening of Parliament, the Metropolitan Police must execute the most secret operation in their armory as they transport the Crown Jewels across London. For decades, the elite squad at Scotland Yard have been in charge of the operation. And for decades, it's run like clockwork. But this year, everything is about to change....

Sherlock Holmes and Dr. Watson seek out their nemesis Dr. Moriarty, believed to be behind the rising tensions between European countries.