The Scottish Highlands. Joshua is walking out in the marshes with a dog and a shotgun. He shoots at birds. A car arrives. It is Vicky. She calls him Uncle Joshua. She wanders through the woods, reading a letter she has written to him, which reveals that she knows of his long affair with her mother, Harriet, having seen her diary. Harriet had vowed to kill herself if ever Joshua's wife Madeleine found out about the affair. When Harriet takes an overdose of tablets, it is Madeleine who Vicky calls for help, but they are unable to save her. Vicky has written all her feelings in the letter, which she now gives to Joshua.

'Aunt' Madeleine is in London. Joshua tells Vicky that he is certain she does not know of the affair. Madeleine is writing her own letter to Joshua, telling him the marriage is over, and that she will stay on in the London flat.

September 1952. Joshua has taken a fishing lodge in Scotland and asked Vicky and Harriet to join him. Madeleine, his bride of six months, travels up later. She already has her suspicions of an affair, which are confirmed when she sees Harriet and Joshua together. She leaves, without saying anything.

Madeleine begins to have her own affairs, with a succession of men, inviting them to the house and sleeping with them under Joshua's own roof, but she doesn't love any of them. As for Joshua, he is always busy with his shotgun. One day, he points it at Madeleine while cleaning it, but doesn't fire. She wonders why not. She hears that Harriet is ill and goes to see her. Harriet is wearing a beautiful Paisley shawl, which was bought on that first trip to Scotland with Joshua. Madeleine tells her that she has always known about the affair with her husband.

Madeleine eschews men for a time and takes up with a young woman protégée. She accuses Joshua of being incapable of receiving love.

Harriet writes her own letter to Joshua, before taking her life. She recalls that she had met him and his wife two years after her divorce from Vicky's father, Ken, and he had been very kind to the newly-single mother. The Scottish fishing trip had been meant as a treat for Harriet and her daughter, but when Madeleine, no longer able to tolerate the cold and wet, left Joshua and Harriet alone together, the affair began. It endured for thirteen years, with Harriet enjoying being loved by Joshua, even though the secrecy began to depress him. Harriet is shocked when she discovers that Madeleine knew the truth all along. She confesses in her letter that she never loved Joshua, just loved being loved by him. She had divorced her husband when she discovered his one act of infidelity, even though he was the only man she had ever loved. She had used the affair with Joshua to stifle her pain.

Vicky drives back to England, not expecting to see 'Uncle' Joshua again.