The review has spoilers&hints in case you havent watched it yet, please go directly to watch the episode .!
The special episode broadcasted on New years eve was different from its other installments because of its setting up in the Victorian age and its inception like treatment may cross over the heads of a numerous no. of viewers but its visual appeal and the performance of the actors is a delight to watch. It will keep you engaged and at the edge of your seat throughout the 128 mins while delightful cunning smart people solving another crime puzzle.
The story revolves around a seemingly dead person arising from death and committing a series of murders where the victims are several unfortunate men who have done some kind of wrongdoing with numerous women throughout their lives.
While it took me a second time to completely get the characters and what actually the plot depicted it may not a thumbs-up for those who didnt praise the Nolans Inception.
In summary I would say you find an extremely capable person solving crime mysteries and an excellent eye for detail which normal people do not posses. Also the extreme power of the Sherlocks brain and fighting everything in the protagonists mind palace is a another brain turner and may not attract its new fans, for others like us yeah we luv the Sherlock theme itself.