In the seventh episode of "Young Sherlock," the narrative begins with Sherlock being shot by Shou'an. As he drifts into unconsciousness, his mind takes him back to the glass jar from Silas's poison demonstration, where a youthful Beatrice calls out to him, asking for help. James rushes to his aid, while Shou'an gives chase to Silas. Mycroft and Cordelia arrive soon after, and Sherlock begs James to stop Shou'an from killing his father.
Mycroft and Cordelia rush Sherlock to a bustling hospital, overwhelmed with victims of the ongoing civil unrest in Paris. Desperate, Cordelia offers the doctor her gold rings and begs him to operate. The surgery is successful, and the doctor removes the bullet from Sherlock's stomach. However, he remains unconscious as Cordelia and Mycroft anxiously wait for him to regain consciousness.
Meanwhile, James catches up with Shou'an before she can kill Silas and reveals that Silas is Sherlock's father. Shou'an admits that Silas is the man she has been hunting all along. The two head to the hospital, but on their way, a policeman attempts to stop them. James shoots the officer to protect Shou'an and is shaken by the man's death, clearly disturbed by taking a life for the first time. Shou'an urges him to focus and reminds him that they need to reach Sherlock.
When Sherlock regains consciousness at the hospital, Cordelia and Mycroft question him about Silas. Soon after, James arrives with Shou'an. She apologizes for shooting Sherlock and finally reveals the truth about the events in China. According to her, Professor Malik had been working on a government-funded research project with Sir Hodge and other Oxford professors.
During his research, Malik discovered a powerful mineral in her homeland that her community mined. The work poisoned the miners, causing many deaths. Malik returned to Oxford and secretly sold the mineral to a private buyer, Silas Holmes. Shou'an explains that Esad works for Silas and was the one who hired her to assassinate the professors, convincing her it would avenge her family and community. In reality, she had been manipulated into eliminating people who might expose Silas's involvement.
Cordelia tells Shou'an that she is free to kill Silas once Beatrice is found. While thinking about how to locate his father, Sherlock recalls Silas mentioning "two corners" when describing where buyers could purchase the poison. He also remembers seeing a matchbox on the cabaret table earlier.
James and Shou'an return to the cabaret bar to delve deeper into the matchbox, discovering it belongs to a restaurant renowned for showcasing the hat Napoleon Bonaparte once left behind. Realizing the potential connection, they head to the restaurant, anticipating Esad or Silas to appear.
As they wait, Shou’an engages James in a conversation about his initial thoughts on killing someone, referencing his earlier reaction. When Esad finally arrives, James follows him discreetly to observe his movements.
Back at the hospital, Mycroft takes the blame for leading Silas to Sir Hodge and decides to return to London. James and Shou’an return with fresh information. James explains that Silas never showed up at the restaurant; instead, it was Esad who met potential buyers.
Sherlock concludes that the only way to lure Silas out of hiding is to pose as a buyer interested in the poison. James adds that Esad is scheduled to meet a potential customer, Duke D’Ormond, the following day.
Sherlock devises a plan where Cordelia will disguise herself as Madame D’Ormond, claiming to represent the Duke. Meanwhile, James takes temporary work at the hotel to intercept the real Duke and redirect him to Sherlock, who will pose as the intermediary handling the deal.
The next day, the plan unfolds seamlessly. Cordelia, in her Madame D’Ormond disguise, approaches Esad while Sherlock waits to meet the Duke. However, the Duke refuses to hand over the payment to Sherlock. James quickly improvises by creating a distraction, allowing Shou’an to steal the money from the Duke’s bag. She passes it to Cordelia, who demands to meet Silas.
Esad leads Cordelia into a private chamber, where he swiftly realizes she's lying. With a threatening tone, he accuses her of deception. Thinking quickly, Cordelia claims she represents a wealthy British investor willing to pay exorbitant amounts for the poison. Esad tells her to return the next day while he confirms Silas' willingness to meet.
Sherlock, James, Cordelia, and Shou'an follow the man and send a telegram to Silas. James intimidates the telegrapher and learns that the message was sent to Constantinople. Meanwhile, Mycroft visits a British ambassador and explains that Silas may possess a devastating new weapon. He requests assistance in bringing Silas back under British authority.
The following morning, Mycroft reunites with Sherlock, Cordelia, James, and Shou’an as they travel to Constantinople. There, Shou’an (whose real name is Xiao Wei) introduces them to her friend Emine. Emine pays a young boy to locate Silas, explaining that the city’s street urchins form a network capable of finding almost anyone quickly.
The boy eventually returns with a message that Silas wants to meet Sherlock alone. During their meeting, Silas offers a deal: He will return Beatrice safely in exchange for Shou’an. Sherlock relays the offer to James, who argues they should hand Shou’an over if it means saving his sister.
That evening, Sherlock spends time with Shou’an, sharing a quiet conversation that ends in a kiss. Though conflicted, he says nothing about Silas’s demand. The next morning, Sherlock meets Silas at a busy market while the others watch from a distance. When Sherlock signals, James escorts Shou’an forward at gunpoint. Silas orders his guards to bring out Beatrice, and Cordelia rushes forward in relief as a young woman appears. But as she reaches the girl, Cordelia realizes that the girl is not Beatrice.
Just then, James hands the gun to Shou’an, who shoots Silas. Before she can fire again, another gunshot rings out, and someone wounds her, allowing Silas to escape into the chaos of the marketplace. As the crowd scatters, Sherlock and Mycroft pull Cordelia away while James tries to help Shou’an escape.
The episode ends with Silas reuniting with his wife and sons. Edie steps forward holding a gun, revealing that she is actually Beatrice.
