Theatre; Pale Horse Royal Court Upstairs, London

The "grieving process" sounds so reassuring, a methodical business you can work through, like the F-plan diet, and emerge from a new person at the other end. It's "all part of it" claims the smugly soothing doctor, when Charlie, a south London hardnut whose wife has just walked in front of a bus, admits to having adulterous sex dreams inappropriate for a novice widower. Even the doctor's professionally fixed smile falters, though, on hearing from Charlie that the fantasy-figure she has glibly termed "the elusive perfect partner" is actually the tomcat he played with as a child.

In Pale Horse - the eagerly awaited follow-up to Some Voices, Joe Penhall's much-lauded first play - black comedy and bleak tragedy bleed into one another, as inchoate grief exposes to this rough diamond the horror of the fact that his life can provide no scaffolding of values for him to cling to. His inarticulate suffering can no more be channelled into prayer (the vicar's suggestion) than be alleviated by the nice "awayday" the doctor recommends.

Admittedly, Charlie's disintegration gets a pretty sizeable boost from external forces. Not many widowers can have found themselves, only days after identifying their wife's corpse, on their hands and knees on Balham Common secretly burying another. This second stiff belongs to a mate and fellow club owner, who is beaten to death with a baseball bat by his abused former girlfriend, Lucy, when he tracks her down to Charlie's failing Wandsworth watering hole, where she has taken refuge as a barmaid. "We could say you done it 'cos you're depressed," is the helpful suggestion of Kacey Ainsworth's excellently game but damaged Lucy. As Charlie becomes complicit with the crime and as the pair drift into bed together, you feel the stage is set for a rerun of Shallow Grave intertwined with Last Tango in South London.

In fact, as the title anticipates, Charlie's despair takes a rather more apocalyptic turn, with the play taking a turn for the worse and never quite persuading you that the beautifully observed initial material can bear the pumping up and belatedly swollen significance. This, however, is no fault of Ray Winstone who, as Charlie, gives a quite outstandingly compelling and authentic performance. Slack-bellied, unshaven, and resembling some dishevelled cross between Mickey Rourke and Bob Hoskins, Winstone glares, judders, and paces around, his stertorous breath shooting down flared nostrils as he tries to control his raging fury at life. If he looks as though he might at any moment explode, he also has the pitiable, haunted aspect of a man whose bearings have suddenly vanished on him and who only now realises the extent to which his marriage had failed.

Played on a dirt floor covered with metal mesh, Ian Rickson's spare, intense, splendidly acted production has a perfect grasp of the drama's seedy atmospheres, whether displaying a slumped line-up of after-hours losers slurring along to Elvis's "The Wonder of You" or evoking post-coital pragmatism in a seaside boarding house. The play itself, though, represents a consolidation of Penhall's talents rather than an extension of his range.

n To 4 Nov. Booking: 0171-730 2554