"The Heat of the Day" is a novel that explores complex interpersonal relationships during World War II, particularly focusing on the moral dilemmas faced by its characters. The protagonist, Stella Rodney, is an attractive English widow who struggles with the shocking revelation that her lover, Robert Kelway, is a Nazi sympathizer. Despite this betrayal, she attempts to protect him from the authorities, highlighting her emotional conflict and loyalty. Robert, a veteran of Dunkirk, ultimately takes his own life after confronting his true nature, which adds a tragic layer to the narrative.

Another significant character is Harrison, an intelligence agent who initially appears affectionate but later shows a sense of relief when Stella plans to remarry, indicating a shift in his feelings towards her. Roderick Rodney, Stella's son, represents youthful enthusiasm and the burdens placed on families during wartime, while Louie Lewis, a soldier’s wife, adds a touch of awkwardness and impulsivity to the story. Additionally, Francis Morris, Stella's relative, plays a crucial role by bequeathing his Irish estate to her son, further intertwining family dynamics with broader themes of loyalty and betrayal amidst the chaos of war. This exploration of major characters provides a lens through which readers can examine the emotional and ethical complexities of human relationships during a tumultuous period.