Preview: The Cryptogram, Donmar Warehouse, London

Mamet's tale of tragedy and betrayal

First staged in 1994, David Mamet's The Cryptogram takes place in the home of a mother trying with a friend to get her restless child to sleep while they wait for his father to come home. For this revival, the friend - in fact, a secretive, duplicitous homosexual - is played by Douglas Henshall, who says: "It's about two adults who are so obsessed with what's going on in their lives that they ignore a child to death."

"The play is mysterious," says its director, Josie Rourke, "but what runs underneath it is a simple tragedy, the disintegration of family and friendship under the pressure of betrayal." She cast Henshall because "in everything I've seen him do, he's been an actor of extreme directness, a thrilling actor. But he also has the ability to make delicate moments shocking."

Those who have seen Henshall act will concur. On television, he has played the wife-beating corporal in Lipstick on Your Collar, Levin in Anna Karenina and Arthur Conan Doyle. On film, he's played the rakehell brother in Angels and Insects (1995), the tattooist whose marriage ends at his wedding in This Year's Love (1999), and the impulsive drifter in The Lawless Heart (2001). Recently, Henshall, now 40, has earned some of his best notices for stage work: as the victim of a witch hunt in The Crucible; the anguished son in Death of a Salesman; the anarchist Bakunin in The Coast of Utopia.

"He's very precise," notes Henshall of Mamet, and has played to stunning effect the role of the son in American Buffalo. "Every word, every gesture is there for a reason, and if you perform it the way he tells you, the language takes off from the page and flies. But my initial instinct as an actor is to elaborate, so the start of rehearsals was very difficult for me... But he's right. You know, if you sit perfectly still in a straitjacket, you're comfortable - it's only when you start thrashing about that you're uncomfortable. I've been thrashing, and I'm only now beginning to settle into my jacket."

12 October to 25 November (08700 606 624; www.donmarwarehouse.com)