Dark and disturbing as it is, Blackbird is also, as the title might gently suggest, an unusual, quirky love story that challenges the usual definition of the genre.

Two of society's forgotten folk, Baylis and Froggy occupy a rundown New York room. Each are dependent upon the other for consolation and care, each immersed in their own private hell. Baylis is a Gulf War veteran in constant pain and quick to sneer at the world's injustice; Froggy, his young girlfriend, has a spiralling heroin addiction. Lisa Lilleywhite's evocative set vividly conjures the dilapidated, dispiriting conditions in which these lovers survive, one fuelled by booze, the other by drugs.

Yet bleak as this all sounds, the beauty of Adam Rapp's excellent and often darkly humorous script lies not only in his keen characterisation, which is masterly, but in the wealth of small details that invest a potentially depressing tale with a poetic, indeed haunting quality that is rarely encountered.

As the play begins, it initially seems as if we've been transported back to the world of Edward Albee's Who's Afraid of Virginia Woolf?. This couple bicker and banter, their mutual insults delivered with real invective. Yet suddenly a bittersweet quality emerges, and you realise that, beneath the raw surface, hides real affection and mutual dependency. It is in the surprisingly tender touches of this unlikely relationship that the play's strength lies.

It might sound mawkish in bold outline, but when Baylis strums an imaginary guitar and sings to a sick Froggy, there's a wistful, lyrical quality present that contrasts sharply with the unremitting gloom of their environment; for a brief moment, ever-encroaching reality is transcended and love poignantly triumphs.

Rapp is fortunate indeed to have secured two first-class performers in the shape of Elizabeth Reaser and Paul Sparks who lend this relationship complete credibility, investing their characters with a humanity that is deeply affecting. The Bush's own Mike Bradwell directs superbly, too.

If you can divest all prior preconceptions of what constitutes a love affair, there's a true dramatic treat in store for you here.

Amanda Hodges