I've always loved this episode from the classic series that illuminated our Saturday nights back in the Autumn and Winter of 1980.
This one deals with a satanic cult - and it's great to see a now-adult Rosalyn Landor playing a similar role to the one she played in the classic Hammer Film 'The Devil Rides Out'.
The story concerns a mysterious ancient mirror which turns up at an antiques fair - and Michael, an art dealer, who unwittingly takes possession of it to get it valued - and then becomes drawn in to the cult, known as the Chorozon Society.
Rosalyn plays Alison, a young woman who's a member of the society but has run away - only to accidentally meet Michael when she literally runs out into the road in front of his car.
The mirror is a 'scrying glass', and has incredible powers - and it just so happens that the Chorozon Society - led by Charles Randolph (brilliantly played by the excellent John Carson), need a willing victim (born on the solstice and in possession of the glass) as a sacrifice to make their devilish Lord Chorozon physically manifest in the human realm...
This whole episode is suspenseful and memorable, and filled with many classic scenes that make this show so distinctive.
There are plenty of twists and turns and deceptions along the way, and you really do wonder how it will all end.
The Chorozon Society themselves are mysterious and secretive - but in real life seem to regular people, whom you would never realize belonged to a satanic cult!
It has just the right atmosphere and tension as it builds up to the story's eventual climax.
There's some good locations around Amersham too, as well as Great Hampden - and look out for an early appearance from the gorgeous Caroline Langrishe as a shop assistant at the antiques shop.
Definitely an episode to watch with a glass of vino (and a little dry bread!)