War breaks out in Tilling as reigning queen of the social scene, Miss Elizabeth Mapp, is usurped by accomplished newcomer, Mrs. Emmeline `Lucia' Lucas.

The Tilling Summer Exhibition provides Lucia with a new battlefield to conquer. With pencils sharpened and easels at the ready, she and Georgie prepare to amaze their new friends with their artistic ability, whatever lengths they have to go to for success. Their triumphs leave Mapp gnashing her teeth with fury until an exotic visitor passing through Tilling provides her with an opportunity to start a new trend. Lucia may have won the artistic heart of Tilling, but Mapp will fight back for their souls and waistlines. Only Georgie's frightful sisters, it seems, can rain on her parade.

While most of Tilling thrills to Lucia's artistic accomplishments, Mapp is convinced that her summer visitor is a crashing fraud and sets out to prove it with her usual vigor.