[4][5] The Moth traces the life of Jack Dillon from childhood to middle age, in a saga that begins and ends in Baltimore, Maryland, with a sojourn in California during the Great Depression.

Dillion comes under unfounded accusations of having seduced Helen, and is forced to flee his home, but not before his father has lost his son's savings in the Wall Street crash of 1929.

An implied sexual encounter between a man in his early 20s and a 12-year-old girl, Helen Legg, prompted Cain's own sister, Rosalie, to caution her brother to remove the scene.

Biographer Roy Hoopes writes: "The James M.Cain who had written about adultery, murder, homosexuality, prostitution, and incest without caring what the studios and book clubs thought was mellowing".

These negative assessments contributed to the poor sales of the novel, leading Cain to remark ruefully that "a simple tale, told briefly, is what people really like".

[19][20] The work is the last of Cain's four novels to feature opera as an element of the story; the others are Serenade (1937), Mildred Pierce (1941) and Career in C Major (1943)[21][22] The 12-year-old Helen appears as a Lolita-like figure, and Dillon's love recalling Edgar Allan Poe's attraction to young girls.

Jack’s relationship with Helen is explicitly healthy, for the protection of her purity is his primary concern; Cain simply recognizes in this athletic American the presence of what might be considered an abnormal desire".

[25] Literary critic Paul Skenazy observes: With one hand Cain seems determined to convince a reader of the fated correctness of this love, while with his other he deliberately establishes his plot around a situation of child and adult that is tantalizing and suggestive.