Sherlock season 3 introduced Mary Watson, John’s wife, but she didn’t stick around for long, and she died in season 4’s premiere episode, with John blaming Sherlock for it – but why? The Great Detective has become one of the most popular and beloved characters in literature and is one who quickly built a very passionate fanbase. Sherlock Holmes was created by Sir Arthur Conan Doyle and made his first appearance in the story A Study in Scarlet in 1887. Sherlock Holmes appeared in a total of four novels and 56 short stories, and they have been adapted to all types of media for over a hundred years.

Among the most recent adaptations is the BBC’s TV series Sherlock, created by Mark Gatiss and Steven Moffat, and which aired from 2010 to 2017. Sherlock brought the detective (played by Benedict Cumberbatch) to modern-day London, and it didn’t forget about other characters from Conan Doyle’s stories, such as John Watson (Martin Freeman), Irene Adler (Lara Pulver), Jim Moriarty (Andrew Scott), and Mary Morstan (Amanda Abbington). This last one is John Watson’s wife in the books, and she didn’t appear in the series until season 3, though how she and John met was never shown, as it happened between seasons.

Related: Sherlock: Why Mary Watson Was Killed Off In Season 4

Details about Mary’s backstory were gradually revealed in Sherlock, and they didn’t match with the version from the books. Mary was an orphan and turned out to be a former assassin with a complicated past, which ended up being an obstacle in her personal life. In fact, “Mary Morstan” wasn’t even her real name, and it’s one she stole five years before meeting John. Mary got involved in some major problems in season 3’s episode “His Last Vow”, where Sherlock found her holding Charles Augustus Magnussen (Lars Mikkelsen) at gunpoint and later shot the detective, and asked him not to tell John. After that, the relationship between John and Mary was fractured, and while they tried to work on it after their daughter was born, Mary’s past caught up with her, and in season 4’s episode “The Six Thatchers”, Vivian Norbury shot at Sherlock, but Mary jumped in the way and took the bullet – and this happened in front of John.

Sherlock season 4 Six Thatchers

As Mary died in his arms, John blamed Sherlock for her death, which many viewers found to be surprising and wrong, as Sherlock was actually trying to save her, and if it hadn’t been for him, she would’ve died earlier. However, John told Sherlock that he “made a vow”, which was to protect Mary, and he did for as long as he could, but not even the Great Detective could have predicted that she was going to take a bullet for him, as they weren’t exactly friends. Going deeper into John’s arc and his relationship with Mary, John also chose to blame Sherlock because he blamed himself. At the beginning of the episode, John was seen befriending a woman he met on the bus (who later turned out to be the third Holmes sibling, Eurus Holmes) and cheated on Mary with her. Knowing that he was not going to be able to fix his relationship with Mary anymore and that he had made a mistake, along with grief, drove John to put the blame on Sherlock.

Other viewers have interpreted John’s attitude to him seeing Sherlock as a “superhuman” who could fix anything – he came back from the dead, got away with Magnussen’s murder, and saved John many times, and Mary’s death in front of them broke that illusion for him. In the end, Sherlock and John got over this and worked together again, and in the series finale of Sherlock came across the biggest threat they had encountered.

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