Downloading subtitles alone is not piracy in most jurisdictions (they are text files, not copyrighted video). However, using them to watch a pirated copy of the episode is copyright infringement.
If you prefer to watch the episode with integrated subtitles rather than downloading a separate file: Sherlock The Abominable Bride Subtitles English Download
If you're looking for a review of Sherlock: The Abominable Bride Downloading subtitles alone is not piracy in most
: If you use VLC Media Player, you can use the VLSub extension to search and download subtitles directly from within the player while the movie is playing. Why "The Abominable Bride" is a Must-Watch not copyrighted video). However