If awards were handed out on the basis of ambition and perspiration, Into the West would collect a shelf-ful. Adapting for the stage a film that by local standards is epic in scope is cheeky enough; doing so with a highly mobile production and a cast of three sounds a lot like hard work.

To be honest, it looks like hard work too. But it's a tribute to the members of Bristol-based Travelling Light Theatre Company that at various times in Into the West their creative energy leaves bits of our disbelief suspended around the tiny Ark theatre.

As most readers will know, Into the West is the story of two (barely) settled traveller kids and their flight on a magical white horse. Adapter and director Greg Banks takes few liberties with Jim Sheridan's screenplay; one of them is to drop the Ellen Barkin character (Phew! says the cast) and another is to turn one of the children into a girl. This is especially welcome, because Cerianne Roberts - apart from having a credible traveller's face - handles the script's high-emotion moments with particularly good effect.

These emotions are, nonetheless, a problem. At such close quarters, the story - of the children's quest for their dead mother and a man's quest for his ability to father - feels distinctly overwrought and definitely over-sentimental. The Sheridan truncheon hits us a few right thumps.

Into the West comes up with fluid and imaginative answers to kids' (and adults') pre-show questions - "How will they do the horse?" "What about the helicopter?" - and a pair of onstage musicians add all the right Celtic notes. If it doesn't add up to the sum of such parts, the fault lies more in the origins than in the execution.