This episode was kind of "meh". Mark Gatiss, who wrote the teleplay, went for comic effect setting the story in 1893 Yorkshire, a year after the second Clara died. People are turning up dead, petrified, and stained crimson, their faces twisted in expressions of horror, hence the title of the episode. The impossible reflection of the Doctor's face in the eyes of the latest victim leads Madame Vastra, her wife and assistant Jenny, and Sontaran manservant Straxx to investigate an organization preaching doomsday and offering the chosen survivors a utopian vision of the future.
As was the case with every episode of Series 7's second half except Cold War, I just wasn't feeling blown away, and I blame that on the diminishing quality of the writing. Head writer and show runner Stephen Moffat keeps promising us big things but always fails to deliver, and that is getting seriously irritating. Neil Gaiman returns to pen the next episode, which features newly revamped Cybermen. I'll let you know how that one goes.