Inside No. 9's The Trolley Problem ending is one of the most disturbing yet

The location this time is a home in the countryside, where psychotherapist Blake (Pemberton) brings an apparently troubled stranger named Drew (Shearsmith), who he found standing gloomily on a bridge during a miserable storm.

Blake appears perfectly comfortable playing doctor at first – despite only having a dubious qualification from 'MacCambridge University' – but the sight of a gun tucked in his guest's waistband compels him to drop a sedative in his drink.

Drew notices, however, and slips his supposedly good samaritan an even stronger dose, with Blake later waking up tied to his oven – and here's where the revelations start pouring out.

Blake hasn't brought home just anyone, but the father of his former patient, Ellie Dawson. In an excruciating recording of one of her sessions, we hear how he took advantage of her vulnerable state and young age to initiate a sexual relationship.

The two continued to see each other for some time, until Blake had a restraining order issued against her, which he subsequently broke on the night she died by fatal overdose.

Blake could have saved Ellie's life by alerting the emergency services, but chose to do nothing – echoing his response to the philosophical 'Trolley Problem' (which fans of The Good Place will be well acquainted with).

Drew is here for justice; at gunpoint, he demands Blake sign a confession and hand himself over to the police. It's a plan that works effortlessly, until the disgraced therapist realises that his captor's weapon is only capable of firing potatoes.

A fight ensues, with Blake gaining the advantage, refusing one last appeal to his humanity before announcing his plan to send Drew off the bridge he found him on. Little does he know that he has just failed a crucial test.

As they're about to depart, Drew asks Blake to retrieve his coat from indoors – why exactly he agrees to do so is beyond me, given what he thinks is about to happen, but he obliges – and is directed to the right-hand pocket.

It contains a piece of paper with a phone number that connects Blake to his son, Robbie, thought to be on a night out, but actually buried alive by Drew in an unknown location.

It dawns on Blake that there's only one man who can tell him where his son is – and he's just doused himself in petrol.

In their short time together, Drew had offered several chances for Blake to confess to his role in Ellie's death and let justice be served, which would have saved his own son's life.

Instead, he refused and even became violent, dooming Robbie to suffocation underground as the only person who could locate and free him self-immolates before his father's very eyes.

Just as Blake did nothing to save Ellie in her time of need, there is now nothing he can do to rescue his own boy from an untimely fate – it's revenge of the coldest and cruelest variety.

Last week's Boo to a Goose also delivered a chilling twist in its closing moments, but The Trolley Problem naturally gets deeper under the skin as a relatively grounded scenario rather than an abstract sci-fi concept.

Beyond that, it's one of those Inside No. 9 endings that cuts to credits at the height of the horror, leaving no time to plant seeds of hope nor to even let us process what's just happened, before we're booted out with existential dread heavy in our heads.

Other episodes that have pulled this eerie stunt include The Harrowing, with its slowly approaching menace, and Mr King, with its twisted folk ceremony – in both instances ensnaring someone haplessly, heartbreakingly unsuspecting, much like Robbie.

There's nothing more powerful than the human imagination, which means that ending the story at this critical moment arguably has greater impact than if they were to depict whatever grim scenes unfold next.

Those are left to us to ponder: the panic felt by innocent, trapped Robbie as his timer ticks down; the unrelenting grief and shame of his father – an immoral character, indeed, but nevertheless human. In either of their shoes, only desolation remains.

Accompanying that lingering trauma is the climactic shot of Drew's flaming body reflected in the glasses of an anguished Blake, with director Al Campbell ensuring its one of the more memorable images in recent Inside No. 9 history.

All these elements come together to create a knockout ending that easily ranks as one of the show's darkest and most disturbing; at this rate, the anthology won't be ending with a whimper, but a terrified scream.

Inside No. 9 continues on BBC Two at 10pm on Wednesday 22nd May 2024. Catch up on iPlayer. Check out more of our Comedy coverage or visit our TV Guide and Streaming Guide to find out what's on.

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