So here it is, the fourth play in John Byrne's “Slab Boys” trilogy - and yes, that is the author's deliberate mistake. In 1978 the first play about young Phil McCann and his mate Spanky Farrell, set in the slab - or colour - room of a carpet factory in Paisley in the late 1950s, was seen widely as the crowning glory of the decade in which Scottish theatre finally found a voice. Fortunately, it has found several other voices since then, for if this rambling, uneven effort is anything to go by Byrne appears largely to have lost his.

Thirty years on Phil and Spanky, now in their sixties, are reunited in the garden of the 15th-century keep in the far North East of Scotland where Phil now lives. Phil's career as an artist has been and largely gone; it's his younger partner, Didi, who is on the Turner Prize shortlist. Spanky is back from the US, where his music career is still stuttering along just enough for him to be shooting a music video. Didi has rented out her house for the shoot because she and Phil need the money but, as it turns out, Didi is sleeping with one of the film crew. With Spanky is the still lovely Lucille, who used to be Phil's wife until he dumped her.

All this catching up on the back-story may be of interest to die-hard fans of the original characters, but it is no substitute for a play. And the clumsy attempts, once we get past the reunion bluster, at revealing the real story of the past 30 years, how the dreams were lived then died, are not much better.

There are glimpses of the old Byrne. “I don't give a toss if it's a deaf mute wi' a chocolate banjo,” says Phil, before he realises that it's his old friend Spanky who's going to be playing in the video. And not many men would get away with a joke about a double mastectomy.

But the rest of Nova Scotia is all over the place. Paul Morrow, as Phil, and Gerry Mulgrew, as Spanky, seem to have only two settings — fast and loud — until the last few minutes of Paddy Cunneen's production. There's a long shouting match between Phil and Didi about conceptual art that comes out of nowhere. Only Gerda Stevenson's Lucille connects with who she was.

There are elements of warmth and humanity in the Traverse production, but one is left mostly with disillusion and despair in place of the lively sense of life needing to be grasped by the scruff of the neck that characterised Byrne's original trilogy.

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