In the fictional Barsetshire of Anthony Trollope during the 1850s, the genial Doctor Thorne is left to bring up his niece Mary. This follows a significant incident during the opening scene between Roger Scatcherd and a Mr Thorne which involves accusations and the violent death of Mr Thorne. Now, decades later, Frank Gresham is in love with Mary but his family needs money—and for Frank to "marry well".

Sir Roger Scatcherd trumps the opposition at the election hustings, but collapses from the ravages on his health due to excessive drink. He is cared for by Doctor Thorne and Mary. More comes to light about her background and Sir Roger grasps the truth. Louis Scatcherd, Roger’s son, is sent for although he clearly cares little for his father, only his money. Doctor Thorne learns that Louis has romantic aspirations regarding his niece and is revolted by the idea. The American heiress Miss Dunstable encourages Frank to continue his romance with Mary; this is in opposition to his family who need money from a match in order to retain their ancestral seat.

Frank's mother, Lady Arabella, along with her sister-in-law, persuades Mary to release Frank from their engagement. The reason she gives is that to hold on to Frank would be selfish and against Frank's best interests.

Louis Scatcherd follows his father's self destructive drinking habit and disgraces himself while at dinner with Doctor Thorne and the Greshams.

Following the pressure exerted upon Mary by Frank's mother, Lady Arabella, along with her sister-in-law, Mary breaks her engagement to Frank. Louis Scatcherd’s drunken rage does not bode well for him. Frank's mother, Lady Arabella, repents. A happy ending at last.