A HELICOPTER crashes at Muddle Farm, Little Muddle, in the remotest South Western countryside.

The only witnesses to the hillside inferno are 17-year-old farmhand Luke (Neil Grainger) and his mother, Avril Pickett (Becky Hindley), for whom life has been harsh on their run-down, isolated farmhouse since Luke's sister, June, drowned seven years ago.

How they wish she could be back with them, how they hope for a miracle, but not for the return of Avril's husband, who walked out on the family for another woman in Basingstoke.

Then, there is a knock on the door. Enter a frightened young woman (Saskia Butler), in her early 20s - June would have been 22 by now - in an orange flying suit. She has survived the crash and is in a state of shock, but there is something deeper than mere trauma here.

She speaks in a most literal manner, walks in a stiff manner and lacks social niceties. She says she comes from Upwards and her name is Sadie, as tattooed on her.

She pleads "Don't let them find me, they mustn't find me". 'They' are brusque Dr Thora Grayling (Alexandra Mathie) and the Army, whose elite rapid response unit must locate a 'weapon' still on board the MOD chopper.

What is the top-security weapon; where is the missing scientist Caroline Forrester; and who is Sadie? Are they all by any chance linked? The plot thickens, as pleasingly and richly as whipped cream, in the latest fantastic and fantastical play for the family by writer-director Alan Ayckbourn.

Sadie is welcomed by the protective, previously hardened Avril like a long-lost daughter; and an increasing bond develops with Luke too, much to the chagrin of his headstrong girlfriend Lisa (Charlie Hayes). All the while, prim Grayling closes in on her quarry, and Captain Leonard Lennox (Justin Brett) and his sergeant (Adrian McLoughlin) lead the bungling crash-site clearance operation, forever one step behind.

This is a classic tender, thought-provoking and amusing cautionary tale from Ayckbourn, with a ring of darkness that recalls Andersen, Dickens and Dahl. The tenderness comes in the budding family relationships and Ayckbourn's championing the triumph of love over evil; the comedy milks the 'strange' behaviour and plain speaking of Sadie and the military incompetence (typified by a running gag involving Captain Lennox's inability to remember correctly any name); and the darkness lies in the dangers of scientific experimentation.

With excellent performances and masterful direction, an engrossing story that marries IT with ET and a happy ending, My Sister Sadie is a superb family drama, social comedy and science-fiction thriller rolled into one.

Updated: 12:24 Monday, December 08, 2003