Fifty-year-old William Whittlestaff becomes guardian to Mary Lawrie, the orphaned and penniless daughter of an old friend, and gradually finds himself falling in love with her. But Mary has already given her heart to the young John Gordon, who has gone to seek his fortune in the Kimberley diamond fields of South Africa. Gordon’s sudden return after a three years’ absence, on the very day of Whittlestaff’s proposal, precipitates the crisis at the center of the story.

An Old Man’s Love is Trollope’s last completed novel, finished just seven months before his death.