I Am My Own Wife, Duke of York's Theatre, London

Not many men can claim to have lived through the days of Hitler's Gestapo and East Germany's secret police while wearing a frock. But the openly gay and transvestite Charlotte von Mahlsdorf - née Lothar Berfelde, the real-life subject of I Am My Own Wife - had the trick of endurance, a talent she was to need right to the end, when her files were opened to reveal what she had done to preserve herself from the wrath of the Stasi.

In the Pulitzer and Tony Award-winning solo show, directed by Moises Kaufman, Jefferson Mays gives an admirably discreet and sensitive performance as this strange figure. Via a tour de force that is all the more impressive for being so unflashy, Mays also plays everyone else. Ironically, the least flattering of his impersonations is that of the dramatist Doug Wright, and at first you may resent the intrusion into the proceedings of this lisping, on-the-make US author, who goes to Berlin on a Guggenheim grant to interview Von Mahlsdorf and recognises a creative jackpot when he sees one. But you quickly come to appreciate that the autobiographical element in the play is an essential part of its honesty.

Wright initially approaches his 65-year-old subject - who devoted her life to preserving and protecting the kinds of culture the totalitarian regimes wanted to obliterate - in the spirit of a hagiographer. But the play becomes a troubled meditation on the slipperiness of the truth. There's no doubt that the transvestite signed an agreement with the Stasi. These agents, though, had quotas to fill. Should we believe her account of the imprisonment of her friend or theirs? Is she a gay hero/heroine or a slightly autistic individual with a skewed sense of priorities, for whom objects were more important than people? In the closing passages, the enigma deepens and human motivation comes to seem a very mysterious business.

Wright laudably withholds nothing, not even his own still-strong desire to put her on a pedestal. "I need to believe in her stories as much as she does," he says. A powerful evening.

To 4 February (0870 060 6623)