Sherlock Season 4 Finale: 13 Dumbest Moments From 'The Final Problem'
8. The Fake Tombstones
In the flashback scenes of Sherlock's childhood with Eurus, we see that he was fascinated by the tombstones. The reason was they had the incorrect dates on, an architectural joke that amused him no end.
Except this was no joke or even flaw from the people engraving the stones, but the work of... yep, Eurus. As it turns out, she was the one who changed the numbers (yeah, a child engraved tombstones, but that's not even the worst bit), all to leave a message for Sherlock to find, which would be a clue to figuring out a song and notice her, forgetting he's about five, and this means he doesn't figure it it out for another 30 years or so. Brilliant.