Jolyon makes a decision that will break apart the close-knit Forsyte family and change his life forever. Winifred married Dartie against her brother and father's wishes, but they are determined to protect the family all the same. Soames is made happy when Irene accepts his proposal of marriage, but she had conditions because she knows she does not love him. June is all grown up and in love with a promising young architect, Phil Bosinney who she is determined to marry.

Bosinney, the young architect, continues construction work on the Robin Hill house for Mr. Soames and his unhappy wife Irene. Soames and Bosinney disagree and ultimately fall out over budget matters, while feelings continue to develop between Bosinney and Irene.

Old Jolyon makes an offer on Robin Hill presuming that Soames will no longer want it. He feels it will be a fitting place for the family and his last days. June meets her father and her extended family for the first time. As Old Jolyon is buried after his sudden death, his family grieves the loss. Dartie is seriously in debt and Winifred finds out.

Soames continues to try and track down where, and with whom, Irene is. Winifred gets the surprise of her life when her husband returns out of the blue. Holly and Val announce they are married and will be moving to South Africa. Soames married Annette and finally he gets a child, but he also loses someone close to him.

Many years have passed since Irene left him and Soames has now decided that he wants a divorce. He's met an attractive young woman, Annette Lamotte, who with her mother runs a restaurant in Soho. He asks Young Jolyon, who is trustee of the legacy his father left her, to ask if she could provide him with grounds for divorce. She assures Jolyon that there has been no one in her life, a message he relays to Soames who refuses to believe it. He even visits Irene but unable to find grounds for divorce, he decides that he wants her back. All he manages to do is frighten her into fleeing to Paris. Val Dartie is disgusted by his drunken father, Montague Darty, who he sees cavorting with courtesans in a casino. Montague decides to abandon his family and leave for Buenos Aires. Soames insists that his sister Winnifred institute divorce proceedings. Val and Jolyon's daughter Holly strike up a close friendship. When they agree to marry, Holly's brother Jolly intervenes challenging him to join the army and go to South Africa.

Soames' hired detective locates Irene in Paris and he again pays her a visit begging her to return as his wife. He is desperate for a son but she flatly refuses him.