The Sign of Three (S03E02)

Sherlock is confronted with his toughest task yet: giving a Best Man’s speech at John’s wedding. However, the day takes a sinister turn as a hidden threat looms over the reception, putting lives at risk before the newlyweds' first dance. Sherlock is tasked with expressing gratitude to the bridesmaids while simultaneously unraveling a mystery and thwarting a potential murderer.