In the programme notes for this play, an article offers the opinion that America’s trailer park population has suffered from bad press over the years and the term “white trash” might be a tad unfair.

There's nothing in Tracy Letts’ dark and decidedly downbeat tale of betrayal, sex, murder and conspiracy to make anyone inclined to that view to rethink their prejudice. Here is a cast of characters totally lacking in any sort of moral compass, who will resort to any extreme to get want they want, or prevent others getting it.

That said, two hours in their company makes for a compelling piece of drama, although you might watch their antics through your fingers.

Drug dealer and user Chris Smith (Adam Gillen) lives in a Texas trailer park with his sister Dottie (Sophie Cookson), their father Ansel (Steffan Rhodri) and stepmother Sharla (Neve McIntosh).

When Chris’ estranged mother steals his stash of cocaine, her son hits on the idea of having her killed and claiming the spoils of a $50,000-dollar insurance policy. It goes a long way to demonstrating the family’s moral position that casual conversation about the plan revolves more around the logistics of getting it done than whether having your mother and ex-wife murdered is quite the thing. Even the simple-minded Dottie, who offers the only glimmer of sweetness in this whole sordid affair, thinks it’s basically a good idea.

Enter Killer Joe Cooper (Orlando Bloom), a detective with the Dallas Police Department who has a lucrative sideline as a contract killer. As the family is unable to pay Joe’s fee upfront, he negotiates a deal whereby he takes sexual favours from Dottie as a “retainer”.

God it’s bleak, with Joe happy to move into the family home and content to have his wicked way with Dottie as the family grow more desperate for the deed to be done. There are moments that raise an occasional laugh, but it’s humour of the blackest hue as this worst-laid plan careers towards the inevitable car crash and culminates in an orgy of violence that borders on the farcical.

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Headliner Bloom conveys Joe’s air of menace through a less-is-more stillness, but never totally convinces as a man who kills for cash and uses everyone in his path for his own depraved ends.

The play really belongs to Gillen and Cookson. Gillen is electrifying as Chris, a coiled spring of frenzied frustration who is about to unravel at any moment, while Cookson gives us a character for whom we can feel a modicum of sympathy in this cesspool of humanity. In fact, it’s Chris’ defence of his sister that offers the one tender moment in the play.

It's hard to find a character with any redeeming characteristics. And yet, like the worst kind of fly-on-the-wall reality show, somehow we can’t take our eyes off them.

Killer Joe is at the Trafalgar Studios until 18 August