Culverton Smith, a prominent entrepreneur and philanthropist, gathers close colleagues, including his daughter, Faith, to confess that he is going to kill somebody.
Mycroft tracks Sherlock's movement across the city, and calls John out of concern, accidentally implying existence of another Holmes sibling.
Smith takes Sherlock and John to his 'favourite room', whilst repeatedly referring to the serial killer H. H. Holmes.
After resuming taking cases, Sherlock discovers the note "Faith" had left him, proving the woman was real.
[3] The villain, Culverton Smith, was loosely based on disgraced British entertainer and charity fundraiser Jimmy Savile, who was a BBC icon.
[4] Sam Wolfson of The Guardian noted that the Savile-esque character must have caused consternation behind the scenes at the BBC.
Wolfson gave "a respectful nod to the BBC," writing, "There must have been some unease in the corporation about having an episode in their flagship drama series in which a beloved public figure... uses his position of power and fame to commit monstrous crimes.
Kaite Welsh of IndieWire graded "The Lying Detective" an A+, particularly the plotline of Sherlock descending into drug addiction: "He really does turn his kitchen into a meth lab, he is weeks away from death and hallucinating.
[7] IGN gave the episode a good rating with a 7/10, describing it as "hampered by another unsatisfying case and some odd story beats".
Club praised the episode and the story, grading it a B+, writing, "'The Lying Detective' does what it does so dazzlingly well that it's easy to overlook its misses...
But just because something checks all the right boxes doesn't mean it totally works, and Steven Moffat's script falls a bit flat where it really counts.