Blindsided @ Royal Exchange Theatre, Manchester, until 15 Feb

Since his breakthrough with Port in 2002, Stockport-born playwright Simon Stephens has come to be recognised as one of the brightest talents in contemporary theatre. Stephens has a unique gift for getting inside the heads and hearts of his characters – often ordinary people trying to keep their balance when life treats them cruelly. With 25 plays to his credit – and a recent Olivier award for his adaptation of The Curious Incident of the Dog in the Night-Time – expectations are high for Blindsided, a third collaboration with director Sarah Frankcom.

What he’s delivered is half of a masterpiece.

The year is 1979. John (Andrew Sheridan) is a trainee accountant with an interest in mind games and occasional house-breaking. He meets Cathy (Katie West), an impulsive, child-like single mum juggling a menial job with a college course. Three days after meeting, they’ve embarked upon an intense, passionate relationship. Cathy’s mother, Susan (Julie Hesmondhalgh), doesn’t trust John. “There’s nothing more horrible than watching your children make mistakes,” observes Susan’s kindly boyfriend, Isaac (Jack Deam). Cathy and John discuss marriage. Catastrophe ensues when a casual betrayal precipitates a horrific and shocking event.

Following the suicide exit of Hayley from Coronation Street, Hesmondhalgh is the woman of the moment, though her role in Blindsided is a supporting one, and the drama mostly rests on the shoulders of young actors Sheridan and West. Sheridan is creepy in a way you can’t quite put your finger on, but it’s West who steals the show, totally inhabiting the character of Cathy. Her love for the undeserving John is purely expressed, and these moments are the play's most moving.

There’s a bigger tragedy at the heart of Blindsided – either shattering or contrived, depending on your point of view. During the second act, the action leaps forward to 1997, and the Isle of Man. The older Cathy, now played by Hesmondhalgh, recalls her lost years with a bizarre fondness. Yes, she’s moved on, but what of the other characters? There’s a fleeting reference to John, still living in Stockport, but as a broken man. Stephens has chosen the easy option, and consequences are conveniently ignored. Given the seismic nature of what happened in 1979, his optimistic resolution seems naïve to the point of being offensive. But this is the Isle of Man, home to motorbike races, cats without tails and Rick Wakeman; clearly, they do things differently here. [Steve Timms]