Episode 6 of "Sherlock & Daughter" kicks off with Lady Violet's blazing fury, sparked by the commotion surrounding the late coachman who attempted to abduct Amelia. Sherlock confides in Inspector Whitlock, outlining his suspicion of a vast conspiracy weaving through the ranks of all coachmen, notably implicating Lord Withersea's driver and the American ambassador's chauffeur.
Within the opulent mansion, Amelia expresses her gratitude to Dan (Michael) for his brave rescue. He seizes the moment, extending an invitation for dinner the following evening, which she gleefully accepts. Just then, Holmes and Inspector Whitlock storm into the room, leading to Dan's temporary incarceration for a day — a strategic move by the inspector to unravel the incident's intricacies, and a serendipitous chance for Dan to visit his father.
Sherlock then unveils Watson's button, discovered in the carriage, to Amelia. As they head back home, they contemplate how Lady Violet might have orchestrated Emma's demise to ensure Clara's ball proceeded uninterrupted.
Sherlock confesses to Amelia that he did, indeed, encounter Lucia Rojas, alias Little Dove in London. During a garden party at the Wild West Show, which he attended with Lady Violet, he stumbled upon Lucia in a tent. Lucia unveiled her designs for the play, leaving Sherlock thoroughly impressed by her profound understanding of engineering. She further showcased her inventions, among them a blueprint for a tank gun. Sherlock now harbors suspicions that this very design might have contributed to her untimely demise.
He clarifies that he withheld this information from Amelia earlier due to an absence of concrete evidence. They deliberate on how this invention casts Lady Violet as the prime suspect in Lucia's murder, given her father's former role as the Secretary of War. As for establishing contact with the mysterious red thread, Sherlock declares his audacious plan: to allow himself to be kidnapped.
Back at the ambassador's opulent residence, preparations for Clara's grand ball commenced with a flurry of activity. Lady Violet, with a glint in her eye, casually mentioned that the esteemed prime minister himself would be grace the occasion! Meanwhile, within the cold confines of the prison, Sherlock orchestrated a meeting between Moriarty and his estranged son, Dan. A heated debate ensued, with Dan, an idealistic soul, voicing his disdain for his father's criminal endeavors, while Moriarty steadfastly clung to his illicit pursuits. Their parting was anything but amicable.
After Dan's departure, Sherlock broached a favor with Moriarty, who agreed on the condition that Sherlock ensured Dan's safety. Shifting scenes to the ambassador's mansion, Inspector Birtwistle arrived, imparting Clara with fresh details about the deceased coachman. He hinted that unless new evidence came to light, the American Ambassador stood to receive a substantial compensation.
Returning to his trusted carriage broker, Clarence, Sherlock discovered that the conveyance used in Amelia's kidnapping was surprisingly recent. With a stroke of genius, he deduced its former life as an ambulance. He then proposed a deal, offering Clarence 20 pounds for his assistance. Just as he was about to depart, Sherlock was abruptly ambushed and whisked away!
Elsewhere, ahead of their dinner engagement, Dan took Amelia to a clandestine club where passionate advocates gathered to petition for universal suffrage, with a particular emphasis on women's rights. Following the inspiring meeting, emotions overflowed as Dan and Amelia shared a tender kiss.
As for Sherlock, he found himself in a secluded room with the Prime Minister. It transpired that Sherlock, through Moriarty's machinations, had orchestrated his own kidnapping to ensure discretion in their clandestine meeting. With gravity, he requested the Prime Minister's signature on a wiretap warrant, empowering Sherlock to eavesdrop on a person of utmost importance.
Back at their base, Amelia and Sherlock delved into the intricacies of the case once more. Sherlock's meticulous examination of the phone records had narrowed down the potential captors' hideouts to five illustrious residences: those belonging to the Earl of Dorchester, the Dowager Duchess of Lincolnshire, Sir Nigel Parks, the Duke of Leicester, and Lady Violet. Sherlock had strategically positioned his trusted allies at each location, each marked by a unique color signal for easy identification.
Their next pivotal action was to activate the Red Thread, setting in motion the rescue of Mrs. Hudson and Dr. Watson. Sherlock subsequently convened with Detective Swann, who was fully equipped with a wiretapping device, ready to eavesdrop on none other than Chief Inspector Whitlock.
Meanwhile, Amelia embarked on a guised visit to Lady Violet's abode, feigning the loss of Clara's fan within its premises. As she meticulously described the fan, cleverly incorporating details about the tank gun's design and a hint of the red thread, Lady Violet's demeanor abruptly shifted, swiftly ushering Amelia out of her house.
Sherlock's subsequent maneuver involved informing Inspector Whitlock of Watson and Hudson's perilous plight, while subtly conveying his proximity to their rescue. Inspector Bullivant and he decided to keep a contingency of officers on alert, awaiting Sherlock's cue. In a dramatic twist, Lady Violet hastily departed in her carriage, unaware that Amelia had stealthily clung to its rear, covertly tagging along, as the episode "Sherlock & Daughter" concluded on a cliffhanger in its sixth installment.