Kenneth More

Fleur begs her father to go to Robin Hill and intercede on her behalf. Once in Irene's company, Soames becomes overcome with feelings about the past. Defending his mother, Jon turns against Soames and shuns Fleur. Heartsick and blaming her father, Fleur shuts herself away until her mother returns home and counsels her to be more practical about marriage.

A renowned philanthropist is murdered but, curiously, not with any of the three weapons at hand. When his daughter's fiance confesses to the crime, Father Brown must divine whether this is the truth.

Having already declared their love for each other, Fleur and Jon wonder about the secret that divides their families. Soames arranges a house party to distract Fleur and pairs her with the dashing Michael Mont for tennis. To please his father, Jon reluctantly agrees to accompany his mother on a three-month holiday abroad, but Irene cuts the trip short when she realizes that the separation from Fleur has only strengthened Jon's feelings for her. Crushed to discover that the flirtatious Profond has turned his attentions to another married woman, Winifred berates Dartie for his years of drinking and gambling.

With the war preparations looming, Winifred takes Dartie back, but he soon returns to his old habits. Winifred goes to her mother for comfort, and Emily responds in the only way she knows. When the Forsytes all gather to see Val and Jolly off to South Africa, only Jolyon manages an honest display of emotion. Soames continues to employ detectives to follow Irene, but even his employees no longer believe that he is only interested in evidence for a divorce. He tracks Irene down in Paris and makes another futile attempt to bring her home. As Irene and Jolyon begin to build a future together, Soames lets go of his obsession with Irene and moves on. With Annette, his dream of a son and heir seems finally within his grasp.