The civility of 1920s Littlehampton, a sleepy English seaside hamlet, is disrupted when a scandal sweeps through town. When the deeply conservative Edith Swan (Olivia Colman) and other residents start receiving anonymous letters filled with hilarious and stupefying obscenities, Edith’s neighbor Rose Gooding (Jessie Buckley), a foul-mouthed Irish migrant, is accused of the crime. If convicted, Rose faces losing her freedom and custody of her daughter. Suspecting that something is amiss, the women of Littlehampton led by Police Officer Gladys Moss (Anjana Vasan), begin to investigate and learn that Rose may not be the culprit. Based on a stranger than fiction true story, this mystery comedy flips a whodunit into who-wrote-it.