While comedic in places, "The Harrowing" makes extensive use of gothic horror elements transmuted into a modern context.

The plot follows Katy (Edwards), who has been hired to housesit for eccentric siblings Hector (Shearsmith) and Tabitha (McCrory).

They tell Katy about their bedridden, disabled brother Andras (Buckley), who cannot speak but will ring a bell if he needs assistance.

Katy is joined by her friend Shell (Rush) once Hector and Tabitha leave, and, upon hearing Andras's bell, the pair reluctantly head upstairs.

The episode takes place in Hector and Tabitha's mansion, which is kept deliberately cold and filled with paintings depicting Hell.

The writers experimented with a variety of possible endings, hoping to make the episode's close both interesting and scary.

Critics agreed that the episode was the most gothic and scary of the series, with journalists writing for The Sunday Times saying that "The Harrowing" would be best avoided by those of a nervous disposition.

On an Empire Online list, "The Harrowing", particularly its final scene, was selected as the 17th best TV moment of the year.

Writers Steve Pemberton and Reece Shearsmith, who had previously worked together on The League of Gentlemen and Psychoville, took inspiration for Inside No.

9 was a "reaction" to Psychoville, with Shearsmith saying that "We'd been so involved with labyrinthine over-arcing, we thought it would be nice to do six different stories with a complete new house of people each week.

9 requires new characters each week, the writers were able to attract actors who may have been unwilling to commit to an entire series.

[1] "The Harrowing" starred Aimee-Ffion Edwards as Katy, Helen McCrory as Tabitha, Shearsmith as Hector, Poppy Rush as Shell and Sean Buckley as Andras.

[5] Comedy critic Bruce Dessau noted that Shearsmith's role was actually relatively minor, saying that the house was the real star.

Tabitha and Hector prepare to inject Katy with a sedative, informing her to remove her blazer and blouse, but she fights back.

Shell says she wanted to be Castiel's new human host, but she is too weak, whereas Katy has the strength of character needed to keep the demon contained.

[6] Despite both reviews characterising "The Harrowing" as one of the weaker episodes of the series, it was called "very creepy" in the Liverpool Echo,[15] and the closing scene was described as extremely scary in the Metro.

[12] Jack Seale, of the Radio Times, said that viewers would "marvel at how [the writers could] pepper the elegant script with gags without breaking the spell".

[6] Nick Rutherford and Keith Watson, writing for the Metro, downplayed the comedy of the episode, saying that "the odd defiantly bad joke ... pierced the darkness".

[16] Due in part to her appearance in the episode, Edwards was shortlisted for WalesOnline's "Daffta" award for best actress, but lost in the public vote to Eve Myles.

Describing the character of Andras, she explained that "Seeing him jerkily moving towards [Katy] with glee, hissing 'mischief'...' straight into camera, is shocking, unexpected, and above all, just horrible.

"Though there are dark laughs in the episode", it was claimed on the website, "the ending is pure nightmare fodder, the babysitter helpless as a Castiel-possessed man advances, hissing, 'Mischief!'