Hero, Theatre Upstairs, Royal Court, London

Liam Garrigan (Danny), Daniel Mays (Jamie), Tim Steed (Joe) (to Johan Persson)

Danny is a young gay primary school schoolteacher who, with his husband Joe, has applied to adopt a child. It's all looking pretty good on that front and the couple are in a state of nervous excitement.

But then Jamie, a less popular teacher at the same establishment and an old, straight college chum of Joe's, arrives seeking reassurance from Danny that he has properly handled a situation at the school in which he was called gay by a seven year old.

Danny responds diplomatically to what was, it's clear, an over-reaction from Jamie that reduced the boy to tears. It's a small incident, but in E V Crowe's Hero – a darkly funny, thought-provoking follow-up to Kin, her debut play set amongst the pre-pubescent girls in a posh boarding school – it snowballs into a scenario that highlights the intolerance still lurking within ostensibly liberal society.

Jamie is subjected to hate-mail by local teenagers who can't even spell “faggot” and then to a bloody homophobic beating. In his distraught lament at the ironic injustice of his predicament, there is the slight but revealing suggestion that for Danny this fate would be not exactly unfair.

Meanwhile, the trouble creates marital dissension. Danny, whose gently inspirational personality is winningly conveyed by Liam Garrigan, decides that he should no longer hide his loving partnership with a man from his pupils.

Tim Steed's more circumspect Joe fears that this would scupper their chances of adoption and confesses – in a way that exposes how hard it can be for homosexuals, too, to shed the prejudices about “normality” that get internalised during a fundamentally biased upbringing – that he himself would have qualms about an openly gay primary school teacher being put in charge of their adopted child.

You want the play to dig deeper into all of this. Instead, though, in the second half of Jeremy Herrin's punchy, traverse-stage production, there's a switch to seeing the events from the perspective of Daniel Mays's more and more outlandishly unravelling Jamie and his underwritten wife (Susannah Wise).

As it touches on Jamie's various reasons for resenting the calmly charismatic Danny and the couple's travails with IVF treatment (dragging in her vague belief in some portentous cosmic shift), the play manages to feel at once too schematically deliberate and unfocused, with gags that sometimes depend on a contrived set-up. Valuable in its raising of important issues, Hero is faintly frustrating in its exploration of them.

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