In the dark town of Grislygust a competition is under way -- The Great Grislygust Grow-off. Marvin plans to grow the tastiest tomatoes in town but his beastly brother, Boris and his poisonous sister, Prunella make fun of him -- "You're a titchy weed, Marvin, and your tomatoes will be tiny too!" But Marvin is determined to prove everybody wrong and soon his competitors will find themselves in BIG trouble