Canary, Liverpool Playhouse

Jonathan Harvey's new play, Canary, takes its title from Peter Tatchell's statement, "Women and gay people are the litmus test of whether a society is democratic in respecting human rights. We're the canaries in the mine."

Spanning five decades of experience as a gay man in Britain, the narrative flits between the present time and the 1960s, moving between Liverpool and London, and dipping in and out of four interwoven lives. Teenage Tom and Billy (an endearingly fresh-faced Kevin Trainor) are closet gays – one of whom, Tom, callously denounces the other and goes on to become a top policeman. Entwined in this eloquent saga, drolly described by Harvey as "our gay friends in the North", is the personal history of Tom's son Mickey, who dies of AIDS, and his winsome lover, Russell.

When police chief Tom is visited by Russell, now a celebrity TV host, determined to out him, the newspapers are hungry for revelations. The events which unfold are touching, funny, brutal and, sometimes, in the case of the policeman's wife (Paula Wilcox), inexplicably surreal.

Harvey hasn't cracked the problem of the act of revenge towards the end of a multi-layered and often confusing plot. The twist feels stuck on and makes an assured piece of writing less convincing. The quickfire dialogue and skein of jokes don't always hit the mark and aren't always sustained by the play's internal dynamic. But what Harvey has tackled is ambitious and important.

The scenes involving young Billy's inhumane treatment at a clinic, aimed at saving him from being a "homeosexualist", is a sharp reminder of how recently terrible things happened here in the name of moral righteousness, and worse, Christianity.

To 15 May (0151 709 4776); then touring to Hampstead Theatre, London NW3 (020 7722 9301) 19 May to 12 June, and Cambridge, Malvern and Brighton