It is 1963. Recently orphaned Anne Marie, a 17-year-old girl from rural Ireland, finds herself pregnant and is promptly dispatched to a local convent by her Aunt and the local curate. There, in the 'Magdalen laundry', she will spend her pregnancy in the company of other women who have in different ways transgressed the strict moral codes that regulate female behaviour in staunchly Catholic Ireland. Once the baby is born, it will be immediately taken from her, either to be adopted or to grow up in the neighbouring orphanage. Her own fate will rest in the hands of her family who can choose to permit her release from the laundry or leave her in the penitential care of the nuns for the rest of her life.

Once inside she is re-named Theresa under the strict regime of Sister Bernadette. Like the other women she is forced to renounce her past identity. Cut her hair and wear the regulation uniform of the laundry where conditions approximate those of a prison - with corporal punishment a familiar feature of coercion.

She is befriended by ex-school teacher Kitty (Bronagh Gallagher), whose 'sin' was to turn down the proposal of marriage her boyfriend made on discovering she was pregnant.

She and Kitty dream of a life together outside the convent with their children.

Kitty strikes up romance with visiting young Garda, Patrick (Gary Lydon) to whom she suggests marriage. Patrick, although at first excited by the idea, later refuses; caught between his deep affection for her and his promising career prospects which would be jeopardised by union with a 'Magdalen' - something he can't afford to do. Devastated, Kitty takes her own life.

When, after the birth of her child, an appeal to her family to 'sign her out' goes unacknowledged, Theresa makes a bid for freedom with her newborn.

Pursued through the streets surrounding the convent she hides in a house, only to be denounced by its owner, a middle-aged bachelor named Frank (John Kavanagh) who subsequently regrets his actions and visits her to apologise.

She implores the older man to intercede on her behalf with her family one last time, which he reluctantly does, only to be refused.

Taking pity on the girl and emboldened by his disgust for her family's cowardice, Frank returns to Theresa and proposes to her. Only eighteen years old she has already borne and given up a child and suffered more psychological and physical hardship than many do in a lifetime. She accepts.

As she prepares to leave, her brother, after a change of heart, comes to the convent and signs her out. Frank and Ann Marie (once again) walk away to begin a new life.