In post-World War I England, Jane Fairchild is a young housemaid employed by the Niven family, who are still grappling with the loss of their sons in the war. Jane's life takes a turn on a warm spring day in 1924, dubbed "Mothering Sunday," a day traditionally dedicated to allowing servants a day off to visit their families. With no family of her own, Jane seizes the opportunity for a clandestine meeting with Paul Sheringham, the wealthy neighboring heir engaged to another woman. As their passionate affair unfolds within the confines of Paul's opulent family estate, Jane and Paul reveal vulnerabilities and desires beyond the societal constraints that define their worlds. This unexpected encounter, set against the backdrop of England’s social structures and lingering grief from the war, becomes a turning point in Jane's life.

Throughout this singular day, Jane navigates complex emotions as she reflects on her identity and future. Meanwhile, at the Niven household, the absence of societal duties allows Mr. and Mrs. Niven to confront their shared history and silent losses. Jane's intimate experience with Paul not only sparks her aspirations for a future beyond servitude but also prompts deep introspection about love, independence, and personal destiny. Unbeknownst to her employers, Jane's delicate balance between her secret affair and her duties illuminates the shifting dynamics in a post-war society slowly moving towards modernity. As the day draws to a close, unresolved tensions and poignant realizations set in motion a change that will reshape her path forward.