The British film "Saving Grace" is an almost perfect example of what happens when a cute idea goes wrong. The cute idea is that a naive, middle-aged woman, Grace Trevethyn (Brenda Blethyn), is widowed when her husband takes a dive from an airplane without a parachute and leaves her with no money and almost $500,000 in debts. They have lived in a lovely Cornwall mansion, where she raises orchids in her little greenhouse and knows nothing of her husband's activities.

Now, faced with ruin and the loss of the house, her gardener Matthew (Craig Ferguson) persuades her to grow marijuana in the greenhouse, so she will make enough money to pay off the bills and keep the house. At the same time, we meet some of the village people -- Matthew's fiancée Nicky (Valerie Edmond), the young doctor (Martin Clunes) -- and other local characters. The doctor and Matthew are inveterate pot smokers, but Nicky, who is pregnant, won't have anything to do with an illegal activity. The film is the story of how Grace and Matthew grow big-time pot in the little old greenhouse and try to sell it in London (Tcheky Karyo in a smooth, witty performance as the charming, cruel French drug kingpin Jacques Chevalier).

The setup is there for either a) an all-out farce, similar to the 1949 British film "Tight Little Island," where everyone on the Scottish island conspires to keep the English revenuers from finding out where the booze is hidden; or b) a more complex study of how a middle-aged widow without resources tries to deal with a life crisis. What happens here, though, is that the writers (Ferguson and Mark Crowdy) and director (Nigel Cole) want to have it both ways, and by trying they've lost it all.

Blethyn, an actress with a fine range that includes a comic feel for double takes and deadpan lines, must here in the film also include legitimate tears, fearful and realistic worries over bankruptcy and disgrace, and the pain of learning that her husband had a long-term mistress. Every time the film starts off in one direction, it quickly lurches into another, yanking us back into the kind of limbo where we don't know what the filmmakers have in mind, and where we cannot give ourselves as an audience to the film. It's a not-uncommon kind of failure, an overreaching, in which the filmmakers think that more is better, when in fact less is more. The greatest comedies simplify to the point of skeletonizing their people; we're told only as much as we need to know for the purposes of the plot. We don't hear about bad marriages or poor sex lives unless they have a bearing on the comedy. Unfortunately, by giving us more than we need to know, "Saving Grace" ends up taking away our pleasure.