Preview: Inside No 9: The Harrowing, BBC2

Draw the curtains, turn off the light. It's the last Inside No 9, sob, and it's a genuine fright fest. In The Harrowing Helen McCrory and Reece Shearsmith play two creepy reclusive siblings, Tabitha and Hector,  who offer schoolgirl Katy (Aimeé-Ffion Edwards) £88 to house-sit for them for eight hours while they have a rare night out. All Katy needs to do is keep an eye on things and, under no circumstances, visit their sickly brother Andras in the top room…

As the horror film poster homage on this page designed by Graham Humphreys suggests, this episode is very much in the vein of classic chillers. I recall a particular seventies monster-in-the-attic film that gave me nightmares for weeks and this might well do the same.

There is no Steve Pemberton this time round and Shearsmith has a relatively small role too. In fact it is the gothic house, festooned with gory paintings depicting scenes from hell, that is the real star. Filmed in virtual darkness, the shadowy pictures plant the seeds and your imagination does the rest of the work. 

Of course there is also comedy here. There is a particularly pithy Michael Jackson joke just when you least expect it. Elsewhere seemingly casual asides instil the viewer with a deep sense of dread and foreboding, such as when Katy wants to use her mobile and discovers there is no signal because the house, as Hector says, is "a dead zone". Great script, though hardly believable. I mean – who in their right minds pays £11 an hour for house-sitting?

And so Inside No 9 ends on an absolute high. This is probably my favourite episode after Sardines. Or A Quiet Night In. Or Tom & Gerri. It really is hard to choose. Almost as hard as it has been to review these self-contained masterpieces without giving away too much. This series has really set an early benchmark to beat for comedy of the year. It has been consistently compelling as each week we entered an entirely different world. While ratings haven't been astounding and have, in fact, dipped to an average of 800,000 viewers a week after a strong start, it is great news for discerning lovers of smartly crafted comedy-drama that there will be a second series. I can't wait for more. In the meantime, sleep well..

Inside No 9, Tonight, 10pm, BBC2.