Life as a Sherlock fan consists of way too much waiting for new Sherlock, and not enough watching new Sherlock. So when the show's one-off New Year's Day special "The Abominable Bride" was confirmed to take place in the Victorian era (when Arthur Conan Doyle's stories were originally published), I was perplexed and disappointed. Sherlock Season 4 won't be premiering until 2017; why waste this precious episode on an alternate universe story that would have no bearing on the ongoing plot? As usual though, there's more to this Sherlock mystery than initially meets the eye. Sherlock's investigation into the case of Emilia Ricoletti is revealed as a deep-dive into his mind palace in an effort to deduce how his archenemy Moriarty could have survived the events of "The Reichenbach Fall" in Season 2. The consulting detective's conclusion? He didn't. Moriarty is really dead, but still more dangerous than any man or woman alive.
Season 3 of the series ends with Sherlock's forced suicide mission to Eastern Europe cut short by a broadcast. Moriarty and his twisted grin takes over every television screen to announce his improbable return with just four words: "Did you miss me?" And since Sherlock stood a foot from him when Moriarty shot himself in the head in "Reichenbach," the criminal's reappearance is indeed a surprise. Sherlock is a show that delights in taking hairpin turns and handing out "aha!" moments for the fanbase to debate and discuss online. The big news in "The Abominable Bride" is that the majority of the holiday special takes place in the few minutes after Mycroft's private jet turns around to deposit Sherlock back on British ground, so that he can save London from Moriarty yet again. But the information that he gathers in those few minutes will be invaluable.
Sherlock isn't one to waste time, so he drugs himself into a stupor to reach a deeper level of consciousness. There, he puts himself into the mystery of Mrs. Ricoletti, her suicide, and the murders that were subsequently attributed to her ghost. Several witnesses had looked on in 1895 when the women stepped onto her balcony, put a revolver in her mouth, and pulled the trigger. If he can find out how she could have committed suicide and been witnessed shooting her husband a few days later, then Sherlock might have solved Moriarty's survival as well. The detective discovers the all-female secret society waging war against the cruel and inconstant men of London, but that solution is a red herring in regards to Moriarty.
The script gives hints that Sherlock is experiencing some kind of Inception-like dream state, like when Victorian Mycroft calls Moriarty "a virus in the data." But it's Moriarty's physical arrival in Sherlock's mind palace that confirms it. Just like the other times Moriarty has crept into his nemesis's thoughts, he taunts Sherlock for his humanity ("The truth is boring.") and creeps the audience the hell out. (“You want your skin fresh, just a little crispy.”) It's this shadow of Moriarty that almost gets the best of Sherlock, so obsessed he is with proving the bad guy to be some kind of demon instead of just a man. Luckily, John Watson is permitted in Sherlock's mind palace too, and together they kill the ghost that's been haunting Sherlock.
Back in the present day, Sherlock's friends aren't thrilled about the whole deliberate overdose thing. Still, he got the information he went in for, and they can't do anything but follow the detective's lead in anticipating future Moriarty chaos. "I never said he was alive," Sherlock clarifies to Mary and John. "I said he was back." Sherlock is sure finally that Moriarty is dead. But he's still the virus. Moriarty is a planner; even in death, he can keep Sherlock Holmes on his toes.