Theatre: Flesh and Blood Lyric Hammersmith, London

In Dearly Beloved, the first of Philip Osment's "Devon trilogy", a smug middle-aged TV producer returns to the small West Country town where he was brought up, his visit exposing and exacerbating the tensions within the tight-knit community there. In Flesh and Blood, the play which now completes the trilogy, another local who has made sort-of-good re- appears in the Devon backwater of her origins with similarly catastrophic results.

Here, however, there are two significant differences. First, the way the new play is structured: a 30-year gap between the acts enables us to see the effect of this catalytic figure on the other three characters before she went off to Australia as well as on her homecoming. The bad news, though, is that the psychological motivation for her return becomes increasingly implausible, leaving you feeling that the play has achieved its tragic symmetries and asymmetries somewhat fraudulently.

Like What I Did in the Holidays, the best segment of the trilogy, Flesh and Blood focuses on a complicatedly riven farming family. Once again, there's a touchy inequality of education among the siblings, a disappointment- bound sister who has had to take on the mother's role and a strong sense of the personal sacrifice exacted by having to slave on the farm.

The play opens just after the death of the tyrannous father. The retarded and deprived Charles, whose awkwardness and frustrated impotence are piteously conveyed in Martin Marquez's fine performance, decides to celebrate not just by using swear words with pointed abandon but by announcing his engagement to Abigail Thaw's Shirley, a girl with a certain local reputation.

The play is excellent as it homes in on the suppressed antagonisms that Charles's bid for freedom brings to the surface. Simon Robson's William, smitten by Shirley himself and still nursing a grudge over a thwarted musical career, opposes the sale of land or the mortgage that would give Charles the money for a fresh start. Stung at being thought of as a desexualised trainee spinster and at being held at gunpoint by him, Geraldine Alexander's Rose lets loose an almost ecstatic volley of humiliating home truths at her deficient brother. To go to Australia with her mother and stepfather seems like the best solution to the newly pregnant Shirley.

Mike Alfreds's engrossing, poetic production - played on a set that seems to expose the interior of the farmhouse to the bleak, snowy surroundings - makes sure that you hear all the distorted echoes of the past when a tanned, laid-back Shirley calls, 30 years later, on this trio (who have aged badly) at their failing farm. But no amount of fine acting and atmosphere can disguise the dubiousness of what we are asked to believe.

The son she had was, it turns out, Charles's, but you feel she would have taken one look at the piteous, electric-shock-treated creature he has become and, for her child's sake, have kept that fact firmly hidden. But here, for a time at least, she is presented as angling to set her offspring up with his inheritance. It's a shame that the last act of this talented trilogy should be built on such a shaky foundation.

n In rep to 27 July. Booking: 0181-741 2311