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.

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

Amelia goes under cover to search for clues at Clara's home; Sherlock goes to prison under pretence of meeting his forever foe, Moriarty.

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

Sherlock searches for the missing jewels and their connection to the kidnapping of his friends; he turns to the insurance investigator, Birtwistle, for his assistance.

After the events at Lady Violet's ball, Sherlock and Amelia are rattled, but as determined as ever to find and dismantle the Red Thread syndicate.