Sherlock: 10 Most Outrageous Fan Theories

1. Various Theories On How Moriarty Returns

Is he back or not? It's a question no one - not even Sherlock - has the answer to yet, with the question most recently being asked in the Series 4 teaser trailer.

Ever since the 'Did you miss me?' video appeared in Series 3, theories and counter-theories have abounded about how a return might work.

One is that Moriarty faked his death, using a real gun but with an empty chamber, and hiding a blood packet in his collar for added effect. Another theory suggests that Sherlock was in on it, with the pair of rivals having an agreement about faking their deaths, as a test to see who can do it more convincingly. There's also the idea that the 'miss me?' screen was faked, either by Mycroft, or some other organisation, or that Moriarty isn't one person, but an entire underground network. Maybe he's really just Sherlock and everything, including us, exists in the mind-palace.

Do you think any of these theories hold any water? Or are they just the work of over-enthusiastic fans? Leave your thoughts in the comments.