You don’t expect to see the dashing star of Pirates of the Caribbean and Lord of the Rings as a near-psychopathic hitman. The fact that it shows him in an unfamiliar light is must be one of the main reasons why Orlando Bloom was drawn to the title role in Tracy Letts’s 1993 play for his first British stage appearance in over a decade.

Letts, who went on to write the Pulitzer Prize-winning August: Osage County, means Killer Joe to be a disturbing experience. An exercise in Texan trailer-park Gothic, it rams sickening horror and outrageous humour together as it pulls us into the morally stunted world of the American underclass.

It’s a devastating attack on a culture debased by poverty and TV-addiction. In the current climate, though, you worry about scenes such as the one in which a woman is forced to perform an act of mock-fellatio on a fried chicken leg, or another in which a 20-year-old virgin with learning difficulties is ordered to strip slowly by the central figure before he has sex with her.

The explicitness (above and beyond the call of duty) shades queasily into the exploitative. You shudder at the play rather than with it during these sequences.

Bloom delivers an impressive performance as the eponymous Joe, a Dallas policeman with a sideline in contract killing. He’s hired by the dysfunctional Smith family to kill their long-divorced mother in the expectation that her life insurance will solve their financial problems. “Look at this way, is she doin’ anybody any good?” asks her desperate dopehead loser of a son Chris (Adam Gillen) who owes money to the mob.

Bloom’s Joe is creepily calm and considered, hypnotic in the measured slowness with which he masks his menacing intent. The controlled swagger of his rhythms is in distinct contrast to all the chaotic kerfuffling of the trailer folk.

When he refuses to work without advance payment, the family agree to give him a “retainer” in the shape of Chris’s damaged, virginal sister Dottie. She’s played here by the superb Sophie Cookson, the character’s simplicity co-existing beautifully with her sudden flashes of clear vision. And until the play’s gratuitous strip, Simon Evans’s production handles delicately the warped echoes of Tennessee Williams’s Glass Menagerie in the scene where Joe, a rather different brand of “gentleman caller”, comes to pay court to the shy, emotionally arrested girl.

I was unconvinced, though, by Adam Gillen, who gibbers at too high a pitch from the start and outdoes the incestuous brothers in Jacobean drama in his deranged jealousy of Joe’s developing relationship with his sibling.

Grace Smart’s set vividly evokes this world in all its run-down grottiness but the production, to my mind, overemphasises the lurid (the trailer-rattling bursts of thunder and lightning; the macabre glare from the TV set that at times surreally suffuses the interior) and fails do proper justice to the uncomfortable laughter that Letts’s text provokes.

Bloom’s fine performance gathers in intensity and by the end he’s in full sinister command of the stage. The normally excellent Steffan Rhodri seems wasted, though, as Ansel, the beerbellied redneck father whose first answer is that “I haven’t given it much thought” when Joe, in the process of molesting Ansel’s wife, asks if he thinks she’s a beautiful woman.

The production will sell out because of its star but, in general, it’s disappointing and leaves the play looking somewhat dated.