The title of Anthony Weigh’s first play – the Australian actor/writer has had the script developed in the National Theatre studio – refers to a state law in Iowa banning sex offenders from living within striking distance of public places where children gather.

The question is, though, where do sex offenders go? The play harps on the metaphor of the pied piper leading the rats away from the town and into the water. What if there’s no water? Weigh suggests we have to find a way of living together, accommodating the rats.

Or, as Joseph Fiennes, thoroughly compelling as the not too bright deputy sheriff, says, “We gotta be safe from ourselves.” It is good to see Fiennes junior on the stage again, but I’m a little mystified over his casting here, as the character is plainly obese and living on free doughnuts.

Weigh’s agile text stumbles a bit in hard-to-follow consequences of the cheap motel going up in flames – the Bush is momentarily raining specks of molten ash – but you can easily relish a quirky look at heartlands American life, with its inbred community of church-goers and little girls pinning up mug shots of sex offenders among their Barbie dolls in pink bedrooms.

In another brilliant Bush design by Lucy Osborne, we start off in the Chicago Art Institute where the shaven-haired piano teacher AG (Ian Hart) is standing in front of the iconic Iowan painting “American Gothic” with a young city boy (Oliver Coopersmith). It’s never established that AG is in fact a paedophile, though his behaviour sets the deputy on his trail.

Back in Eldon, Iowa, Fiennes reports to the house of Byron and Nan (Roger Sloman and Phyllis Logan) who play the grim puritan couple with the pitchfork in Grant Wood’s painting each year in the small town festival. He serves an eviction notice on AG, who lodges there (Schumann’s kindergarten music wafts plangently through the kitchen), and sets off with him to an unspecified destination in his prowler van.

Josie Rourke’s production never quite clarifies the play’s meaning until an extraordinary bedroom scene between the tensile, troubled Fiennes and the confident pre-pubescent girl (Charlotte Beaumont) who’s playing with fire as an innocent avenger. There’s a hint of the witch-hunt here, from Arthur Miller’s Salem to Rebecca Wade’s The Sun. And a clutch of fine performances includes Kirsty Bushell’s slatternly motel manager.

- Michael Coveney