The mood of The Return of the Soldier is initially luxurious and hopeful but gradually becomes mournful and pessimistic. At the outset of the novel, Jenny is very secure in her place within her family and society. She enjoys living at Baldry Court, maintaining the house's luxurious atmosphere, and upholding ideals of British country life; and she finds these activities meaningful because she sees herself as creating "a fine place for Chris"—in other words, a comfortable domestic life for a cousin with whom Jenny is implicitly, if never openly, in love.
Chris's memory loss and the revelation of his relationship with Margaret are extremely destabilizing events for Jenny and thus shift the novel's mood dramatically. While the love affair violates all social conventions to which Jenny subscribes, it's also the only authentic relationship in the book. Understanding the intensity of their love, Jenny is extremely jealous of Margaret but is also forced to question her upper-class lifestyle for the first time. At this point in the novel, she's torn between a desire to forget about Margaret and return to the uncomplicated family life she once enjoyed, and the hope that Chris's memory loss will prove permanent, allowing him to escape from the army and find happiness with Margaret.
When Chris inevitably regains his memory and loses his relationship with Margaret, the novel's mood of romance and potential disintegrates, and so does Jenny's confidence in her way of life. Jenny sums up this collapse when, watching Chris after his parting with Margaret, she sees him look at the house as if it were "a hated place to which, against all his hopes, business had forced him to return." Margaret's obvious moral superiority causes Jenny to view her life's work—taking care of Baldry Court and creating a comfortable domestic life for Chris—as worthless, since her cousin so obviously desires life with Margaret instead.
And since Chris's relationship with Margaret is totally incompatible with his class status as a wealthy, landed businessman, Jenny can no longer take comfort in being a member of the upper class as she once did. By the end of the novel, Jenny is not only fearful of modern horrors like WWI and nostalgic for an earlier, "unspoiled" era, but unsure if the way of life she once prioritized has any value at all
