A theatrical miniature with maximum impact, Unsuspecting Susan is a spare and affecting one-woman play by Stewart Permutt that begins on a familiar enough path but ends up taking a detour to a far more disturbing place.

This is, of course, a territory well mined by Alan Bennett, whose Talking Heads theatrical monologues set the benchmark of surprise and insight for the form, with his speakers seeming to be making discoveries about themselves even as they are sharing them with the audience.

But Permutt has a distinctive and quirky voice of his own, with a gradually darkening edge to his writing that reveals an individual putting a brave face on things despite her world collapsing around her.

Susan Chester is a Hampshire housewife and landscape gardener, divorced from husband Colin and living alone with her two dogs, Sally and Eros. She belongs to the village amateur dramatic society, and this month she's starring in a production of The Killing of Sister George, but her co-star can't seem to learn her lines.

Susan is also fretting over her absent 32-year-old son, a depressive who has made several suicide attempts but is now happily, it seems, living with another man, an Egyptian called Jamal in a flat in Victoria.

Susan's dogged insistence that they are just flatmates - and incredibly tidy ones at that - immediately nods a wink at the audience that she's actually in denial about the true nature of their relationship. Unsuspecting Susan also seems to be the kind of play in which their move to a new place in north London - "they found a place in Willesden" - gets a ready laugh.

Permutt, however, conceals far more surprising - and uncomfortably topical - revelations than that, though to reveal more here would be unfair. Suffice it to say that he's created a peach of a part for that wonderfully characterful character actress Celia Imrie. Not only is she a consummate comic performer, but she also excavates beneath the comic surface to reveal real pain and anguish.

She is beautifully directed by Lisa Forrell with the kind of unobtrusive intimacy that forges an immediate bond between storyteller and audience and makes this 80-minute monologue haunt, resonate and grip as fiercely as a full-length work.

- Mark Shenton