Belfast, 1920. Connie Wintour, a protestant English aristocrat, is haunted by the loss of her brother, Harry, at the battle of the Somme, and is suffering from a depression which threatens to lapse into severe mental illness. Sombre and passive, she feels trapped by her bourgeois lifestyle and persecuted by the doctors and nurses who treat her. Her only emotional outlets are the letters she writes to her dead brother, which she hides among his things in his old bedroom.

Wintour, Connie's father, is an industrialist with a large shipbuilding concern in the city. He claims not to care about the difficult political climate, but is concerned by the increasing civil unrest, which is beginning to affect his business. Against his daughter's wishes, he participates in an Orange order march and political rally, and becomes a target for sectarian violence. As a result, the British army are called in to defend his estate, encircling it in barbed wire. For Connie, this is a disturbing reminder of the trenches where her brother died. She submits to a treatment of hypnotherapy, which unearths terrible nightmares.

Connie meets the bluff, plain-speaking Lieutenant Ryder at an army social gathering at her father's house, and finds him an interesting conversationalist. Their encounters become more frequent and their discussions centre around the ethics of war and soldiering. Later, running away from another party, Connie introduces Ryder to the secret world of her brother's room. But she infuriates him with her naïve sympathy and he explodes in anger. She flees onto the Belfast streets, which are rocked by explosions and gunfire, and witnesses a pair of republican insurgents being shot by British soldiers. Dazed, she retreats into a nearby Catholic church. When she returns home the following day, her condition worsens and she falls into a near vegetative state, refusing to speak or eat.

Ryder decides to get out of Belfast, but he returns to the Wintours' house one final time to make amends with Connie. After hearing about her deterioration from her angry father, he wanders round her brother's room and discovers the hidden letters, which Connie continues to write. He reads them and is deeply moved by her sadness and her sensitivity to his own situation. At her sickbed, he begs her to speak to him, in desperation burning the letters to try and get a response. But Connie has given up hope and is damaged beyond repair. As her father runs for parliament in the soon to be partitioned Irish government, his daughter wastes away at home, force-fed and incapable of further resistance.