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. But she has her own ideas and follows her intuition closer to answers but even closer to danger.

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