The episode kicks off with Michael Wylie, alias Daniel Moriarty (portrayed by Joe Klockey), in a tense confrontation with Amelia Rojas (played by Blu Hunt). His voice vibrates with urgency as he demands an explanation for her assault on him. She, in turn, counters with a question of her own, wondering why he has relentlessly hunted her down. After a moment of mutual standoff, he agrees to holster his weapon if she pledges not to attack him again. She nods, a reluctant accord, and he reveals a crushed bouquet, offering it to her as a gesture of peace. Amelia hesitates, querying the reason behind the flowers. He replies, seeking to alleviate the discomfort of their first encounter and renews his offer. She finally accepts, uttering a thanks and introducing herself. He follows suit, and their hands meet in a tentative handshake. He then broaches the subject of needing her assistance, to which she suggests he might require the services of Sherlock Holmes (played by David Thewlis). He clarifies that Sherlock was instrumental in incarcerating Professor James Moriarty (Dougray Scott). Amelia firmly declines to spy on her mentor. He then proposes a pound for any information on whether Sherlock intends to level additional charges against Moriarty.
Meanwhile, at Baker Street, Sherlock arrives home, his thoughts preoccupied with Amelia. Mrs. Halligan (Mary O’Driscoll) expresses her dismay at his bossy demeanor towards Amelia, unaware that she is Sherlock's maid and assistant. The revelation causes Mrs. Halligan to sway with shock. Mr. Halligan (Ardal O’Hanlon) catches her just in time, explaining that the idea of Amelia being entangled in a harrowing kidnapping scandal horrifies her. Sherlock is in the midst of apologizing when Amelia enters the scene. Mr. Halligan tends to Mrs. Halligan, offering comfort.
Amelia updates Sherlock on a job offer from Marjorie Anderson (Ivana Milicevic), which involves escorting Clara Anderson (Gia Hunter) to various events. She mentions that Bertram Birtwistle (Shashi Rami) has also approached her about becoming his apprentice. Sherlock mocks Bertram as a "pompous ass" and encourages her to accept Marjorie's offer. Amelia expresses empathy for Charlie Holroyd (Hyoie O’Grady). Sherlock reveals that Charlie, before his demise, had imparted the aliases of his accomplices, Magott (Michael Ellen Sean) and Weams (Andy Kellegher). She presents him with her sketches of Magott and Weams and inquiries how he managed to visit Charlie unnoticed. Sherlock confesses to enlisting the help of an inmate, in exchange for locating his son, Daniel. He insists that Amelia carry a gun during her hunt for Magott and Weams. Amelia handles the firearm with practiced ease, crediting her mother, Lucia Rojas (Savonna Spracklin), for her training. A memory flashes before her eyes—Lucia teaching her the art of shooting. Amelia suggests waiting until she is married, implying that a husband would protect them. Lucia, however, believes they should always be prepared to safeguard themselves.
Noticing a man's print on Amelia's disarrayed dress, Sherlock deduces that her assailant had overpowered her. He questions why Lucia never taught her to defend herself physically. Amelia responds by recounting how she fought off an older man who tried to steal Chance. Sherlock accepts her narrative and outlines her next mission.
At the Withersea Coffin Factory, Mr. Halligan voiced his disapproval of her entanglement in the kidnapping saga, expressing hope that his wife remained unaffected by it. He characterized Sherlock's methodologies as unconventional and cautioned her against crossing Mrs. Halligan. Noticing Lord Withersea's (Jack Meade) carriage in the vicinity, she hastily darted into the charred remnants of the coffin factory. Lord Withersea lambasted the fire inspector (Brendan Farrell) and threatened to expose him unless he departed promptly. Summoning Scotland Yard's Chief Inspector Whitlock (Aidan McArdle), Amelia informed the fire inspector, feigning concern, that her brother was employed there but had fallen ill. He assured her that the factory would resume operations on Sunday. In a hurry, she exited and implored Mr. Halligan to trail Lord Withersea's coach on its way to Richmond.
At Scotland Yard, Detective Swann (Antonio Aakeel) showcased to Sherlock their latest investigative tools, including an electrical lighting fixture, and boasted about their handwriting analysis capabilities. Shortly thereafter, Whitlock announced to Sherlock that he was now leading the investigation into the missing jewels and vowed to uncover them. He demonstrated how the telephone could be utilized to apprehend a railway passenger. Sherlock mused that a telephone could have spared him a trip to prison to confront Moriarty, who was in search of his estranged son, Daniel. Whitlock revealed that Daniel had adopted the name Michael Wylie and was employed by an Australian stockbroker. Pretending interest in a residential telephone, Sherlock requested to examine the invoice detailing outgoing calls. Upon departing, he sought Swann's assistance.
At the Withersea Estate, Amelia persuaded Mr. Halligan, albeit reluctantly, to dispatch a telegraph to Sherlock, informing him of Lord Withersea's Richmond estate. She coerced him by offering Sherlock's two sovereigns for the telegraph and lunch. Scaling a rocky wall, she found herself confronted by a formidable dog. Commanding it to sit and stay, the dog obeyed promptly. Meanwhile, at Baker Street, Sherlock offered a group of local lads two shillings each to locate Wylie, to which one boy protested, stating they were no longer eleven. Sherlock sweetened the deal by offering an extra half crown if they found him by sundown the next day. Mrs. Halligan handed him the telegraph, while a man, observing from a nearby coach, offered half a crown to ensure he wasn't followed before hailing a cab. The boys cleverly delayed the man's coach for two crucial minutes.
At the Withersea Estate, Amelia stumbled upon two coffins tucked away in the carriage's recesses. With determined force, she pried open their lids to reveal Weams and Maggot, both lifelessly slumped from gunshot wounds. As eerie voices echoed in the distance, she sought sanctuary in the nearby shadows. Withersea, cool and calculated, instructed O’Leary (Seamus O’Hara) to discreetly dispose of the corpses. O’Leary’s sharp eyes caught sight of Amelia’s coat dangling on a nearby hook, and Withersea inquired whether he had dared to open the coffins. O’Leary, unwavering, shook his head and whistled, summoning a hound that traced her scent to a cozy haystack. Commanding her to rise, O’Leary’s stern visage loomed over her.
In a moment of vulnerability, Amelia confessed that her mother, Lucia Rojas, was a casualty of the infamous Red Thread Syndicate. Withersea, feigning ignorance, dismissed her claim. O’Leary, fingers itching on his trigger, threatened Amelia’s life before turning his wrathful gaze upon Withersea. Just then, a hackney cab deposited Sherlock at the estate’s entrance, who promptly began scaling the imposing security gate despite the driver’s protests about his advancing years. Sherlock, playfully claiming to be a spry 40, was interrupted by a sudden gunshot. The cab driver sped off, leaving Sherlock to dash towards the stables where he found O’Leary lifeless and Amelia clutching a firearm.
Her voice trembling, Amelia narrated O’Leary’s aggressive confrontation, but Sherlock, interrupting gently, assured her of his understanding. He noted Withersea’s presence indoors and, upon inspecting the coffins, breathed a sigh of relief that Mrs. Hughes and Doctor Watson were spared this grim fate. Taking a soothing sip from his flask, Sherlock commended her bravery and apologized for placing her in peril.
Sherlock retrieved O’Leary’s firearm and marched towards the manor. Withersea, engrossed in a telephone conversation, was startled by Sherlock’s abrupt entrance. With gun drawn, Sherlock demanded to know if Amelia was his spy. Admit it or not, Sherlock presumed as much. Withersea, composed, vowed not to mourn O’Leary’s demise. Sherlock’s astute observations Withersea’s gambling-induced bankruptcy. He proposed a deal: sparing Withersea from prosecution in exchange for Watson and Hughes’ liberty. Withersea, warned of the Red Thread’s immense power, saw no escape and took his own life. Sherlock pocketed a Royal Telephone and Telegraph Company invoice, clues piling up.
Back at Baker Street, Sherlock revealed to Amelia that his investigation now zeroed in on Moriarty’s son, Michael Wylie/Daniel. Her mind flashed back to her encounter with Wylie, and Sherlock, sensing her turmoil, granted her a day off but urged caution. She thanked him for his unexpected kindness. Lady Violet Somerset’s (Fiona Glascott) arrival interrupted their moment. Sherlock weaved a tale about Watson’s Italian escapade and Hudson’s Scottish Highlands family visit, masking the truth.
Lady Somerset imparted grim news: Withersea had slain O’Leary before ending his own life, leaving two corpses in the stables. Marjorie sought Amelia’s services as Clara’s chaperone for her societal debut, arranged by the Ambassador. Scanning a Wild West show photograph, Lady Somerset pointed out herself, Sherlock, and Little Dove (Lucia). Her recollections revealed Sherlock’s request to pass Lucia’s design to her father, the Ministry of War’s head. She unveiled a Pinkerton Detectives telegraph detailing Amelia’s birth, eighteen months after Lucia’s London departure, with Lucia reporting her father deceased. The intrigue deepened, each revelation weaving a tapestry of secrets and deceit.
