Having unmasked the Red Thread syndicate, Sherlock and Amelia must confront their enemies at the most anticipated debutante ball of the season, where secrets will be revealed, hearts will be betrayed, and more than one shot will find its target.

The game is afoot! Having cracked the code of the Red Thread's communications network, Sherlock, Amelia, and their friends are hot on the path of the kidnap victims, chasing a trail of breadcrumbs that leads all the way to the vaults of the Bank of England. 

As Sherlock and Amelia identify the villains surrounding them on all sides, Holmes repays a favor to his oldest enemy, arranging a meeting between Professor Moriarty and the young Australian man who has suddenly become very close to Amelia.

Determined to keep Amelia out of harm's way, Holmes sends her back to the relative safety of undercover work. While Holmes searches for answers about the missing jewels, Amelia learns that in this society, the most dangerous place for a lady may just be a debutante ball.

Amelia withholds details from Holmes after encountering a charming man with a pistol, but Sherlock must step in when her investigation turns fatal.

Amelia goes undercover to search for clues at Clara's home, while Sherlock goes to prison under pretense of meeting his forever foe, Moriarty. 

While Sherlock chases a stolen carriage, he sends Amelia on a hunt across London. But she has her own ideas and follows her intuition closer to answers but even closer to danger.

Blackmailed and sidelined from investigating, Sherlock Holmes finds hope when a young woman arrives on his doorstep, potentially holding the key to solving the kidnapping of an ambassador's daughter.