This is a one-woman show for two people. The one woman is Nana, both the mother of the playwright and a mother figure for us all. The second person, simply called the narrator, is the playwright himself, the brilliant Quebecois writer Michel Tremblay whose short and very sweet play is a eulogy to the woman who set him on his creative career but never lived to see his success.
The phrase "if only" haunts the play. If only she'd lived longer. If only they'd been able to speak more honestly. If only she hadn't suffered. But despite the undercurrent of wistful regret, there's nothing maudlin about Tremblay's beautiful comedy. He pays tribute not to the death, but to the life of his mother, in a way that is funny, affectionate and very true.
He is aided by Eileen McCallum, a figure of jovial authority in blue floral dress and apron, who captures the subtle combination of unlettered intelligence, extravagant imagination and lack of self awareness that makes the character so recognisable. Playing opposite a restrained and dignified Peter Kelly on a plain stage - just two swivel armchairs and an arc of sky-blue fairy lights - she negotiates the transition from forceful parent to vulnerable old lady with noble grace. "It's no fun describing things the way they are," she says, investing her son with the transformative gifts of his craft.
Written in 1998, 30 years after Les Belles-Soeurs, Tremblay's breakthrough debut, If Only feeds on the audience's knowledge of a superb body of work. Tremblay didn't just revolutionise the theatre of Quebec: in the tremendous Scots translations of Bill Findlay and Martin Bowman of plays such as The House among the Stars and Solemn Mass for a Full Moon in Summer, he has made a major contribution to Scottish theatre as well. That his mother didn't live to see any of this, makes If Only all the more poignant.
Finally, with a stunning coup de theatre, Tremblay gives his mother his ultimate accolade: the gift of theatrical immortality. It is a mark of his genius that at the last minute he turns a moment of sad introspection into an act of generosity that sends the audience living, breathing, loving into the night.
· Until April 12. Box office: 0131-248 4848.
