Luna Gale (Hampstead Theatre)

"I love children, which is why I never had them," says Caroline, the divorced care worker, in Rebecca Gilman’s troubling new play which marks director Michael Attenborough‘s return to the venue he ran (before the re-build) in the late 1980s.

Caroline, played with a febrile, concentrated energy and a wide array of coloured shirts by Sharon Small, is dealing with ninety cases at once, contemplating early retirement to her country bolthole, fretting over the impending departure of a "miracle" client called Lourdes and is faced with a complicated new problem.

That problem is the child, the unseen Luna Gale, not yet crawling, whose parents, Karlie and Peter, are a pair of useless alcoholic crystal meth addicts and whose grandmother, Cindy (Caroline Faber), now divorced from Karlie’s step-father, has "kinship care" of the child whom she has "baptised", egged on by her evangelical pastor boyfriend Jay (Corey Johnson).

Karlie and Peter – compellingly played by newcomers Rachel Redford and Alexander Arnold; she’s freaking out when the play starts, he’s a placid zombie – are good adverts for people who shouldn’t be allowed to have children. But Gilman takes a more optimistic point of view.

Getting Luna Gale back entails co-operating with Caroline’s false imputation of child molestation (of Karlie) by the stepfather. Turns out this shocking tactic is down to Caroline’s own back story, and we’re suddenly in a crazy world – our own, in fact – where everyone’s a victim and the accusatory finger whirrs around indiscriminately.

Attenborough’s well-acted production catches this mood of witch hunt, piety and paranoia in Cedar Rapids, Iowa, to something like perfection. Public denunciation only makes things worse – check The Crucible – when Caroline’s immediate boss, a sanctimonious, box-ticking suited creep (Ed Hughes), links up with the pastor to pray for her salvation, hands on each other’s shoulders.

Cindy, a nurse’s assistant, has decided that the only reality is "the heavenly truth" whereas Caroline believes in the possibility of the parents changing and that good foster care can be a catalyst, not an end in itself. Karlie, at least, has signed up to Mothers off Meth (or, MOM). And Peter suggests that a residual sense of decency and responsibility is not beyond recall.

It seems that child abuse has been a national issue in the States for much longer than here, and the play worries about the scale of the problem, and the bureaucratic tentacles engulfing it; Lucy Osborne’s brilliant, expensive-looking design places quick-changing, evocatively detailed interiors against a mountainous semi-circular library of case-files and paper work, reinforcing a sense that liberal concerns are well-placed and that old-time religion is no answer.

Luna Gale runs at Hampstead Theatre until 18 July