What is it? A comedy about cancer.

Why you’ll love it: No, wait, come back. It’s not just about cancer. It’s also about kidnap, attempted murder and sexual assault.

No, wait, come back. It’s actually really good. Ill Behaviour is the story of Charlie, a well-adjusted family man recently diagnosed with Hodgkin’s lymphoma. Charlie wants to forego traditional treatment in favour of natural remedies, to the dismay of friends Joel and Tess. So Joel and Tess come up with the most sensible plan available to them: renting a mansion, turning it into an illegal hospital, abducting Charlie without telling his wife or kids and injecting him with a series of chemotherapy drugs against his will. There, that sounds like a side-splitting laughathon, doesn’t it?

Admittedly, cancer is starting to become a mouldy trope of a plot device. It’s everywhere, which can be especially galling if you’re actively trying to avoid the subject for whatever reason. Characters in Twin Peaks have cancer. Characters in The Leftovers have cancer. There’s cancer on EastEnders, cancer on This Is Us, cancer twice over on House of Cards. There’s been cancer in Breaking Bad, Fargo, Stranger Things and Mad Men. It’s getting to the point where a cancer reference on a television programme now simply feels like an exploitative shortcut to tragedy.

Fortunately, Ill Behaviour is one of the few shows to actually earn its cancer storyline. The disease is encoded into every scene and line of the series. It is the driving force behind everything that happens onscreen. We see the effect the disease has, but we also see what chemotherapy takes out of a person, and how it affects those around the sufferer. Sam Bain, the Peep Show co-creator who wrote the series, deserves vast amounts of credit for that alone.

Even more fortunately, he’s managed to craft a taut, funny, relentlessly immoral thriller out of it. Although the kidnapping starts from a place of good intentions, it gets messier with every step. Tess and (especially) Joel absolutely believe that they’re saving their friend’s life by abducting him, and every awful thing that comes from it – tying him to a chair, lying to his wife, faking emails, molesting him, chasing him with a crossbow – is seen as a necessary obstacle to be navigated. Aiding them in this wrongheaded undertaking is Lizzy Caplan who, as an alcoholic sex-addict doctor with substance abuse issues, finally gets to play the most Lizzy Caplan role that has ever been created.

The undoubted star of the show, though, is Chris Geere’s Joel. Starting as a lovable loser, who handily happens to find the means to fund this madcap scheme, he gradually turns into the very worst kind of monster. All the characters are in denial about something here – illness or feelings or addiction – but Joel is a masterclass in broken nostalgia. He behaves abysmally in the second half of the series, smashing through ever-higher levels of abject despicability, all because he can’t accept that life moves on. By the time he has revealed a certain piece of body art, he is little more than a wasp in a jar, thrashing uselessly against something he can’t see. And yet he never manages to become truly unlikable, thanks in equal parts to the character’s innate stupidity and Geere’s slippery performance.

The delight of Ill Behaviour comes from just how intractable things get. Bain seems to get a perverse kick out of digging himself into ever deeper holes, only to somehow discover a miraculous escape route. The result is a tight, rip-roaring three hours of television that even the most meticulous cancer-avoider will find satisfying.

Where: BBC iPlayer

Length: Three hour-long episodes, streaming from Saturday.

Standout episode: As a character piece, Ill Behaviour takes a lot of setting up. Episode two is where things really start to motor.

If you liked Ill Behaviour, watch: The Wrong Mans (Netflix), Breaking Bad (Netflix) Stuart Heritage