Sherlock killed Magnussen to protect Mary. Mycroft witnessed his brother's actions, but it happened too fast for him to intervene. With the entire incident captured on police surveillance, even Mycroft, a high-ranking official in the Prime Minister's cabinet, was powerless to protect him. The only option was to send Sherlock on a mission to Eastern Europe as a way to atone for his crime. Everyone knew the immense risks involved, and they prepared for a permanent farewell. However, just minutes after takeoff, Sherlock was recalled. A more severe national security crisis had emerged, one that only Sherlock could resolve.
In a classified MI6 office, national security cabinet ministers with the codenames "Antarctica," "London," and "Love" listened to Mycroft's briefing. For unknown reasons, Moriarty's image had appeared on all media screens across Britain, repeating the chilling question, "Did you miss me?" Moriarty was a high-intellect criminal with a vast network. Despite his confirmed suicide, the security services couldn't afford to be complacent. As Moriarty's old adversary, Sherlock was the obvious choice to lead the investigation. Meanwhile, to provide an explanation to the judicial authorities, Mycroft altered the police surveillance footage, attributing Magnussen's death to an accidental discharge from a nervous officer on the scene.
Sherlock sat disinterestedly through his brother's presentation, as if it were all irrelevant. The thrill of regained freedom excited him far more than the three powerful bureaucrats before him; he preferred chatting with Vivian Norbury, the minute-taker sitting in the corner. Lady Smallwood, codenamed "Love," who had approved both Sherlock's exile and his recall, finally lost patience. She was not there to tolerate Sherlock's antics; she wanted to know Moriarty's next move and Sherlock's strategy. Sherlock's answer stunned everyone in the room: wait. Instead of guessing blindly, he advocated watching and waiting, ready to act as events unfolded.
For Sherlock, the greatest joy in life was sitting in his chair at 221B Baker Street, immersed in a sea of crime, reveling in the thrill of solving cases. His time in custody had created a backlog of pleas for help. Sherlock's mind raced day and night, solving cases at a frantic pace, forcing John and Mary to repeatedly remind him to rest. Not long after, John and Mary's daughter, Rosamund Mary Watson, was born. Molly and Mrs. Hudson were the godmothers, and Sherlock was, naturally, the godfather. Even during the christening, Sherlock was incessantly texting, investigating cases. Molly could only look on helplessly at this man whose intelligence quotient utterly eclipsed his emotional quotient. Life soon revolved around the baby, with even Sherlock occasionally tasked with babysitting.
Time passed busily without any sign of Moriarty's promised threat, until Inspector Lestrade arrived with a new case. Weeks earlier, at the 50th birthday party of Cabinet Minister David Welsborough, David received a video call from his son, Charlie, who was on a graduation mountain-climbing trip abroad and couldn't return. The signal seemed poor; Charlie's video froze, leaving only audio. Charlie asked his father to take a picture of his car, specifically a Power Rangers toy stuck to the front grille. Dismissing it as a childish whim, David took the photo, sent it, and then Charlie fell silent. Assuming a lost connection, David thought little of it until a week later, when a drunk driver, evading police, crashed into Charlie's car parked in the driveway. A fuel leak caused a fire. After the blaze was extinguished, a charred body was found inside the car. DNA tests confirmed it was Charlie, and the time of death was approximately a week prior.
After reviewing the autopsy report, Sherlock quickly formed a theory. Two types of synthetic fibers found in the driver's seat suggested Charlie had bought seat covers and disguised himself as one. He likely planned to jump out and surprise his father when he came to take the picture but died suddenly from an epileptic seizure or heart attack. Thus, for a week, no one noticed Charlie disguised as a car seat, until the accident revealed the gruesome truth.
What truly caught Sherlock's attention was an empty space on a small round table in David's study, amidst photos and memorabilia of Britain's first female Prime Minister, Margaret Thatcher. Scratch marks indicated a missing plaster statue. David mentioned a previous break-in where a Thatcher statue from that table was smashed on the porch. The intruder had broken in at night and deliberately smashed the statue under the lighted porch. Sherlock believed this elaborate act was more than simple vandalism, though the reason eluded him. This might be the first piece of Moriarty's puzzle, or perhaps not; he couldn't be sure, but his intuition screamed that something was coming.
Soon, a second and third statue were smashed, with the perpetrator's blood found at one scene. Sherlock attempted to use bloodhounds to track the scent, but the cunning culprit had walked through a messy market and a bloody butcher's area, confusing even the best hounds. This failure only fueled Sherlock's determination. He contacted his hacker friend and discovered the smashed Thatcher statues were a limited Georgian edition of only six. Three were destroyed, leaving three with known owners. Then Lestrade called: another incident. This time, two more statues were smashed, and their owners murdered. With five statues destroyed, the sixth became the target. Sherlock decided to lay a trap.
That night, a figure infiltrated a mansion, moving silently towards the final Thatcher statue on a desk. Sherlock, lying in wait, turned on the lights and confronted the intruder. Pulling off the black hood revealed a man of Central Asian appearance. Sherlock was skilled in combat, but the man, Ajay, was equally proficient. After a fierce struggle, Sherlock gained the upper hand. To his disappointment, Ajay knew nothing of Moriarty, and the statues contained no black pearls sought by Interpol. Inside the shattered statue was only a USB drive marked "AGRA" – identical to one Mary once possessed. Sherlock was stunned. When Mary's past was revealed, she had given such a drive to John containing her identity documents, which John had burned, wanting to leave the past behind. How could it be here? Ajay saw Sherlock's recognition and realized this man knew the woman who had betrayed their cell. Before police surrounded the building, Ajay escaped, vowing to kill the traitor.
Sherlock met Mary privately in a remote location. Seeing the drive, Mary was shocked. Her real name was Rosamund, and she was once part of a four-person cell codenamed "AGRA" from their initials. To ensure loyalty, each held a drive containing all members' identities. Six years ago, during a Georgian coup, the British ambassador was taken hostage. AGRA was hired for the rescue but received a last-minute call changing the plan. The caller knew the code word "Amo," forcing AGRA to adjust, walking them into a trap. Only Mary escaped. Believing her team dead, she left that life and married John. From photos on the drive, Mary identified her attacker as Ajay, a teammate she thought long gone.
Hearing Ajay wanted her dead, Mary was disbelieving until she saw Sherlock's seriousness. Fearing for John and Rosamund's safety, she made a swift decision to leave. Drugging Sherlock, she took the drive, left a farewell note for John, and fled. She constantly changed identities and locations, never staying long. Despite this, Sherlock and John found her at a small Moroccan hotel. The drive contained a tracker she hadn't anticipated. Sherlock had vowed to John to protect Mary and wouldn't let her face danger alone. John, a soldier at heart, wouldn't hide at home while his wife was in peril.
Suddenly, Ajay appeared, having followed Sherlock. He revealed that after Georgia, pursued, he hid in a plaster factory and hid his drive in the base of a drying Thatcher statue. Even under torture, he never talked. For six years, he listened for escape chances, hearing only his torturers yelling "Amo" and guards mocking him for being betrayed by the Englishwoman, "Rosamund" – Mary.
Mary faced Ajay's six years of rage, hoping honesty would win his trust. But she never got the chance; police responding to the scene shot Ajay dead from behind. Mary lost another comrade. But Sherlock latched onto Ajay's clue: "Amo" is Latin for "Love" – the codename of Lady Smallwood, who was also the liaison for the AGRA operation. This couldn't be a coincidence.
Sherlock called Mycroft, who risked arresting Lady Smallwood. But the evidence – a voice and a codename from a phone call – was flimsy. Mycroft had recommended AGRA, and Smallwood had no motive. Sherlock had to admit he'd acted rashly. If not Smallwood, who else knew the Georgian code word? Calming down, Sherlock realized the answer: someone easily overlooked yet omniscient – the minute-taker, Vivian Norbury.
Learning from MI6 that Vivian was at the aquarium, Sherlock alerted John and Mary. Before backup arrived, Sherlock entered. In the dark underwater tunnel, he found Vivian, who knew her time was short after Smallwood's arrest. Mary arrived second; hearing Vivian's voice, she identified her as the woman who changed their plans. Vivian, exploiting her position, had long sold secrets. Discovered by the ambassador in Georgia, she panicked, but the coup provided a chance to silence him. She tipped off the rebels and altered the rescue plan, sending the team to their deaths. She thought everyone involved was dead, but two AGRA members survived, exposing her.
Mycroft and Lestrade arrived with police, alerted by John about the security breach. Seeing backup, Sherlock relaxed, misjudging Vivian's character, assuming she'd surrender. He was fatally wrong. Desperate, Vivian drew a gun and fired at Sherlock. Mary leaped in front of him, taking the bullet.
John, who had just dropped off Rosamund at Molly's, arrived to see his wife fatally wounded. Watching her die, John was devastated, blaming himself for failing to protect her and hating Sherlock for breaking his promise. Sherlock was consumed with guilt, searing "Norbury" into his memory as a permanent reminder to never underestimate a situation.
Mary's death devastated both Sherlock and John. John couldn't bear to see Sherlock, who threw himself into work to numb the pain. Among piles of mail, a DVD case labeled "Did you miss me?" caught his eye. It wasn't from Moriarty, but a posthumous joke from Mary, knowing it would grab his attention. The disc contained her final message, sent after her death, asking Sherlock to save John Watson – a request that presented him with his most difficult challenge yet.