SPOILER ALERT! DO NOT READ IF YOU HAVEN'T WATCHED SUNDAY NIGHT'S EPISODE OF SHERLOCK.
The fourth season of BBC's Sherlock came to a dramatic conclusion on Sunday night as Sherlock, Mycroft and Watson found themselves pushed to their limits in a dark game set by Sherlock's sister Eurus. The Final Problem saw Sherlock (Benedict Cumberbatch) and John Watson (Martin Freeman) confronting Mycroft (Mark Gatiss), who has kept Eurus' existence a secret from his detective brother.
The trio head to Sherrinford, the high security island prison where Eurus is kept, to discover how she escaped, only to find that she has laid a trap for them. Forcing them to take part in a series of twisted 'puzzles' set in different rooms, it's a race against time as Sherlock tries to solve the mystery and save all of their lives.
Sherlock, Watson and Mycroft faced off against Eurus in the dramatic finale
Fans were left distraught during the tense episode, particularly when Eurus forced Sherlock to call close friend Molly and convince her to confess her love for him, threatening to blow up Molly's home if he didn't. "NOT MOLLY" trended on Twitter throughout the hour-and-a-half episode, while many fans expressed sadness for the lovesick heroine.
The show's loyal following was also left shocked after being led to believe that dastardly villain Jim Moriarty had returned from the dead, making his grand entrance to Queen's hit I Want to Break Free as he arrived in Sherrinford to team up with Eurus. His appearance proved to be a flashback scene, but it didn't stop fans from going wild for the twist.
Marking the season's finale, the final few moments saw John Watson's deceased wife Mary sharing one last video message from the grave for her husband and Sherlock, in which she nicknamed them 'My Baker Street Boys' in a final goodbye. This caused a frenzy amongst fans on social media, who celebrated the fitting tribute and praised the emotional scene.
However, some also began to express concerns that this may have been the last ever episode of Sherlock – a fact that writers Mark Gatiss and Steven Moffat have neither confirmed nor denied.