In a quiet corner of London, Watson and Mary's family welcomed a new life - their lovely daughter Rosa.They invited Sherlock as their godfather. However, during the baptism process, Sherlock seemed absent-minded, only sending and deleting messages, which made Watson and Mary feel a little confused.

Meanwhile, a video call came in from David's son Charlie, who insisted that David take photos of the family's car, despite the spotty signal.A week later, a car crashed into Charlie's car, causing an explosion and Charlie's body was found inside the car, more than a week after his death.This bizarre case aroused Sherlock's great interest.

Sherlock discovers a photo of Thatcher, Britain's only female Prime Minister, in David's home, which arouses his vigilance.He intuitively believed that this photo was inextricably linked to the upcoming case.Through investigation, Sherlock discovered that a burglary had occurred at home, and the broken statue was a key clue.

After some reasoning, Sherlock revealed the truth: Charlie wanted to give David a surprise, but died accidentally.The conspiracy behind this is far more complicated than it seems.Sherlock begins an in-depth investigation, trying to uncover the truth hidden behind it.

During the investigation, Sherlock found his brother Mycroft and asked about the relationship between Moriarty and Thatcher.He had a premonition that something was about to happen, and it all seemed to have something to do with Mary.

At this time, Jinlis approached Sherlock, hoping that he could help solve a case.Sherlock had already told everything he wanted to know before Kinlis could speak.Kinliss was surprised by Sherlock's insight, but also regretted his wife's departure.Sherlock tells him that his wife left because of his harsh tone.

The police officer delivers a statue that arouses Sherlock's suspicion, and blood is found on it.Sherlock and Watson found the hacker Toby who had helped him, hoping that he could provide technical support.At the same time, Sherlock also invited Mary to participate in the investigation, and they took Toby to search for relevant evidence.

Greco found the clue between the statue and Thatcher, while Sherlock was always paying attention to the Black Pearl incident.While waiting for the murderer by the pool, Sherlock was pushed into the pool by the murderer and tried to drown him.After a fierce fight, Shylock successfully escaped the murderer, but found Agra's note the moment he broke the statue.It's all about Mary, and Sherlock is determined to protect her.

However, things develop beyond Sherlock's expectations.Mary left a letter to Watson and left without saying goodbye. She came to Tehran, Iran, by rolling dice.Sherlock follows, hoping to find Mary and solve the mystery.In Dehradun, Sherlock, Watson and Mary reunited. However, the appearance of Ajie broke the warm atmosphere.

Ajay and Mary faced each other with guns, and Sherlock learned from their conversation that the betrayer was an Englishman.In order to uncover the truth, Sherlock meets Mu from the private assassination organization at the London Aquarium.Ammu said she was tired of it all and just wanted peace, just like Mary.However, Mary firmly disagreed with Amu's request.

During the tense confrontation, Amu picked up a pistol and pointed it at Mary.Sherlock takes decisive action and reveals Amu's true identity.Faced with an inescapable situation, Ammu had no choice but to shoot at Sherlock, but Mary blocked the shot for Sherlock.With Mary's sacrifice, Sherlock and Watson were able to escape from danger.

However, Mary's death brought great sorrow to Watson, Sherlock and Mrs. Hudson.While sorting out Mary's belongings, Sherlock and Mrs. Hudson accidentally discovered Mary's suicide note.In her suicide note, Mary asked Sherlock to save Watson.