Wicked Little Letters follows the story of deeply conservative English local Edith Swan and her community as they are targeted by wicked letters filled with unintentionally hilarious profanities. The blame falls on rowdy, foul-mouthed Irish migrant neighbor Rose Gooding, leading to a national uproar and a trial. As Police Officer Gladys Moss and the towns women take matters into their own hands to investigate the crime, suspicions arise that Rose may not be the true culprit after all.