Set in a 1920s English seaside town, WICKED LITTLE LETTERS is a mystery comedy based on a true story involving two neighbors: the conservative Edith Swan (Olivia Colman) and the rowdy Irish migrant Rose Gooding (Jessie Buckley). When Edith and other residents receive anonymous letters filled with hilarious profanities, Rose is accused of the crime, leading to a national uproar and a trial. However, as the town's women, led by Police Officer Gladys Moss (Anjana Vasan), investigate the case themselves, they begin to suspect that Rose may not be the culprit.