Sherlock: The Sign of Three

Sherlock struggled with the speech because expressing personal emotions didn't come naturally to him. The speech required him to articulate deep feelings about John Watson, his friend and flatmate, which Sherlock found far more challenging than solving complex crimes. Additionally, he was simultaneously trying to solve a murder plot targeting Major Sholto while delivering the speech, dividing his attention between emotional vulnerability and urgent detective work.

Mrs. Hudson warned Sherlock earlier that marriage redraws a person's lines, hinting at the emotional complexity he would face.

The Bloody Guardsman case involved Guardsman Bainbridge found stabbed in a locked shower stall with no weapon visible and no obvious way in or out. The mystery perplexed Sherlock because the wound remained hidden until the belt holding Bainbridge's uniform loosened, revealing the stiletto blade that had been concealed within it. The case remained officially unsolved, but Sherlock used the details during the wedding to illustrate John's compassion when John detected a pulse and saved Bainbridge's life.

The case served as both a narrative device in Sherlock's speech and a crucial clue linking to the later murder attempt.

The Mayfly Man was Jonathan Small, the wedding photographer. He was targeting Major Sholto as revenge for a failed military operation in Afghanistan that killed his brother and other soldiers under Sholto's command. Small killed recently deceased single men and impersonated them to form relationships with women who worked for Sholto, nurses, gardeners, and security guards, gathering intelligence and planning his attack on the wedding day.

The Mayfly Man case was introduced through flashbacks showing Sherlock and John investigating a nurse named Tessa who reported dating a ghost.

Major Sholto was targeted because he was the sole survivor of a devastating Afghanistan incident that killed his entire unit, including Jonathan Small's brother. Sholto had been living in seclusion under constant threat from media scrutiny and death threats. Small chose the wedding as the perfect opportunity to kill him, knowing Sholto would attend and would be in a public, vulnerable position.

Sholto's arrival at the wedding was met with mixed reactions, and Sherlock noted the danger his presence posed.

Sherlock identified Jonathan Small as the Mayfly Man by connecting several clues: the women who dated the 'ghosts' all worked for Sholto in various capacities (nurses, security, gardening), and Mary’s intimate knowledge of John, including his middle name Hamish, suggested someone from Sholto’s close circle. Sherlock realized the photographer had access to the wedding venue and the ability to get close to Sholto. He also linked the Bloody Guardsman stabbing as practice for the actual murder attempt.

Sherlock’s deduction built upon earlier observations about Mary’s knowledge and the pattern of women connected to Sholto.

Major Sholto attempted suicide because he was overwhelmed by guilt over the Afghanistan disaster that killed his brother and other soldiers. He had been living in seclusion under constant media scrutiny and death threats, believing his continued existence brought danger to those around him. When Sherlock's note revealed that the murder attempt had been discovered, Sholto loosened his own belt in a suicidal gesture, seeing death as the only escape from his tormented existence.

The episode established Sholto's heavy burden as the unit's sole survivor and his fragile mental state.

Sherlock deduced Mary was pregnant by observing three key signs: increased appetite, a change in taste perception, and morning sickness. During the first dance, he revealed these observations to John and Mary, confirming that his famous powers of deduction extended beyond crime scenes to everyday life. The revelation brought joy to the newlyweds but also underscored Sherlock's bittersweet awareness that his closest bond with John would inevitably change.

This moment represented the final emotional turn of the episode, shifting from suspense to bittersweet revelation.

Sherlock's note to Sholto warned him of the impending danger, the fact that a killer was targeting him at the wedding. The note prompted Sholto to return to his hotel room and prepare a pistol for self-defense. When Sherlock, John, and Mary rushed to the room, they found Sholto armed and on the verge of using the weapon on himself, demonstrating how the note both warned of external threat and inadvertently triggered an internal crisis.

This scene directly led to the tense confrontation in Sholto's hotel room.

Sherlock recognized that John's marriage to Mary would permanently alter their friendship dynamic. With Mary pregnant and the couple beginning their own family, Sherlock understood he would no longer be John's primary relationship. This realization came as a bittersweet moment at the episode's end, while celebrating John and Mary's new chapter, Sherlock felt the profound loss of his former closeness with his best friend, leading him to leave the reception alone with a weighty, solitary resolve.

Mrs. Hudson and Mycroft both warned Sherlock earlier that marriage would change things in unforeseen ways.

The Bloody Guardsman, Bainbridge, was stabbed with a stiletto blade that was concealed within his own belt. The belt held the blade in place, hiding the wound from immediate view. Only when the belt loosened later did the wound become visible, creating the illusion of a locked-room mystery. Sherlock explained this method to connect the case to Jonathan Small, who had staged the stabbing as practice for his planned murder of Sholto.

This explanation came during the tense hotel room confrontation as Sherlock pieced together the overall plot.