This book draws the focus back onto a single character, Anne and Gilbert's youngest daughter Bertha Marilla "Rilla" Blythe.

It has a more serious tone, as it takes place during World War I and the three Blythe boys—Jem, Walter, and Shirley—along with Rilla's sweetheart Ken Ford, playmates Jerry Meredith and Carl Meredith—end up fighting in Europe with the Canadian Expeditionary Force.

The book is dedicated: "To the memory of FREDERICA CAMPBELL MACFARLANE who went away from me when the dawn broke on January 25, 1919—a true friend, a rare personality, a loyal and courageous soul."

At some point after Montgomery's death in 1942, publishers quietly trimmed Rilla of Ingleside of a few thousand words, removing among other things passages containing historically accurate but now offensive anti-German sentiment.

Rilla's brother Walter, who is of age, does not enlist, ostensibly due to a recent bout with typhoid but truly because he fears the ugliness of war and death.

Rilla's father Gilbert challenges her to raise the war orphan, and although she doesn't like babies at all, she rises to the occasion, eventually coming to love "Jims" as her own.

Rilla grows much closer to Walter, who some townsfolk and fellow students have branded a slacker, an insult he feels deeply.

As the war continues, one night Dog Monday begins to howl inconsolably, leading the family to fear something terrible has happened to Jem.

In Walter's last letter to Rilla, written the day before his death, he tells her that he is no longer afraid and believes it may be better for him to die than to go on living with his memories of war forever spoiling life's beauty.

Finally the family receives a telegram: Jem had been taken prisoner in Germany, but eventually escaped to Holland and is now proceeding to England for medical treatment.

Noting that Kenneth Ford has survived the war but has not contacted her, Rilla concludes that his interest must have faded and she should consider joining the college-bound group.