Sherlock: The Sign of Three

DI Lestrade and Sergeant Donovan stand at the cusp of arresting the Waters family, who have repeatedly evaded the police. Yet a text from Sherlock prompts Lestrade to abandon the case and rush to Baker Street, where Sherlock expects the worst and calls for maximum backup. The twist is that Sherlock is merely preoccupied with a best man speech for John’s wedding.

On the morning of the wedding, Mrs. Hudson reminds Sherlock that marriage changes people. The warning sits alongside the growing commotion around John's big day. Sherlock steels himself to perform his duties as best man despite his wandering thoughts.

At the reception, John is delighted to see Major James Sholto, his former Army CO, who has been living in seclusion after Afghanistan-related threats. Sholto’s presence hints at dangerous scrutiny around the wedding. Sherlock calls Mycroft, who echoes Mrs Hudson’s line that the marriage will change John’s life.

Sherlock rises to give the best man’s speech but hesitates, and the crowd is left waiting. Flashbacks roll, recalling the Bloody Guardsman case where Bainbridge appears stabbed in a locked shower stall and no weapon is found. John’s actions later reveal his compassion by saving Bainbridge.

Sherlock recounts the Bloody Guardsman case: Bainbridge was stabbed with a stiletto blade whose belt concealed the wound until the belt loosened. The combination explains how the wound remained unnoticed until the right moment.

John’s careful examination of Bainbridge reveals the living guard’s pulse, saving him, while Sherlock notes this act of compassion stands in contrast to the unsolved murder. The episode uses this contrast to illustrate how ordinary action can outshine unresolved crime.

Sherlock recalls the Mayfly Man case: a nurse named Tessa investigated a deceased man and claimed to date a ghost. Sherlock and John, drunk from John's stag night, are arrested for their antics while trying to solve the mystery. They deduce the killer impersonates recently deceased men to lure women.

Sherlock realises all the women who dated the 'ghosts' worked for Sholto in various capacities. The Mayfly Man’s plan is to strike at the wedding by targeting Sholto, who isolates himself from media scrutiny.

Sherlock slips a note to Sholto with crucial information, prompting Sholto to return to his hotel room and arm himself with a pistol. Sherlock, John, and Mary rush to the room to intervene before harm can occur. The tense moment tests the bond between the expectant couple and their friend.

In a decisive turn, Sherlock confronts the wedding photographer and identifies him as Jonathan Small, the Mayfly Man. He explains the photographer’s collaboration with his brother to kill or threaten Sholto, and how the attack on Bainbridge was practice. The room tightens with fear and resolve.

Sherlock expounds on Bainbridge’s wound as a stiletto blade routed through a tight belt, explaining why the stab went unnoticed until later. The deduction links the earlier Guardsman case to the Mayfly plot against Sholto and the wedding. The danger escalates as everyone races to protect Sholto.

After catching the culprit, Sherlock plays the violin for John and Mary’s first dance and reveals Mary’s pregnancy. He lists her morning sickness, increased appetite, and taste changes as signs, reassuring them they will be good parents.

Despite the joyous news, Sherlock leaves the reception alone, realizing his relationship with John will never be the same. The episode closes on a quiet, somber note as he contemplates the future without the same closeness.