Grace Trevethan (BRENDA BLETHYN) is a middle-aged woman living in a quaint seaside village on the Cornish coast. A recent widow, Grace has just learned that her late husband racked up a considerable amount of debt and even took out a second mortgage on their three-hundred year old house, all to fund some ultimately unsuccessful business ventures. To make matters worse, he was also having an affair with Honey (DIANA QUICK), a woman from London.
Everyone in the small town knows of Grace's financial difficulties, but despite their efforts to help her out, the creditors continue to arrive and remove her belongings bit by bit, and it looks like she'll eventually lose her home. Even her gardener and all around handyman, Matthew (CRAIG FERGUSON), decides to stay on with her, despite his last check bouncing.
When Matthew asks Grace, who's known for her lovely greenhouse and proficient green thumb, to look after some ailing cannabis plants he's been covertly growing with his fishing captain girlfriend, Nicky (VALERIE EDMOND) and the town's local physician, Dr. Martin Bamford (MARTIN CLUNES), the two suddenly hit upon an idea. If Grace could bring his sick plants back to life, they could then sell the lucrative marijuana and raise enough capital to pay off her debts and save her home.
Converting her formerly traditional greenhouse into a marijuana factory, Grace and Matthew set out to do just that, despite Nicky's objections and the possible criminal ramifications of doing so. Nonetheless, they manage to keep their operation secret from the local lawman, Sgt. Alfred (KEN CAMPBELL), although most everyone else in the town eventually gets wind of what they're doing.
With the pot now ready to be harvested, Grace then sets out to find someone who will buy it. As her venture eventually involves international drug dealer Jacques Chevalier (TCHÉKY KARYO) and his henchman China McFarlane (JAMIE FORMAN), Grace races to unload her stash before the various creditors seize her home or the police figure out what she's up to.