I wasn't.
A woman, Hannah Altman, who runs a pub and doubles as an organist, is killed when a magic trick goes wrong at a fundraiser for the local church. It wasn't an accident; it was murder. The police decide that Gideon the magician was the intended victim.
Now, magic done in a church has to be controversial, which it is here. So it's no surprise that Gideon was the recipient of hate mail comparing his act to Satanism. A elderly curate, Andrew Maplin, is the loudest critic.
There are figures wearing robes who hold rituals outside of Gideon's mansion. The mansion was owned in the 19th century by a known pagan. One of these robed people kills the curate Andrew and leaves his corpse on the altar.
There are the usual adulterous affairs, which open those people up to suspicion, and a relative of the pagan is uncovered - living in the present.
Barnaby and Nelson carefully investigate and this time, even Sarah Barnaby gets into the act of asking questions until the murder by magic is solved.
One reviewer on IMDb thought this episode made fun of Christianity and another thought there were too many black people. I would say it was not particularly reverent toward some of Christianity, but certainly a scriptwriter is allowed to present that point of view just as we are free not to like it.
As far as too many black people, the producer gave an interview saying the following: "We don't have ethnic minorities involved. Because it wouldn't be the English village with them. It just wouldn't work...We're the last bastion of Englishness and I want to keep it that way." He was suspended for that comment and ultimately stepped down as producer.
The reviewer's point was that the had no objection to bringing black people into a show, but only if it's realistic and not just to be politically correct. Again, I can understand that, but I also understand that black actors need jobs and better yet, opportunities to get them. This show has been running a long time and employs a lot of people. I don't think it's a sin to include blacks or any other ethnic group. You can consider it nontraditional casting or color-blind casting, which is done at the National Theater.