During the funeral service for Tom Garner, the much-hated president of the Chicago & Southwestern Railway Company, called the greatest railroad in the country, Henry, his elderly secretary and friend from childhood, leaves the church in an emotional state and returns to the railroad office where he places into his pocket a picture of Tom as a young man holding his son.

At his modest home after supper, Henry talks to his wife about Tom, whom she despises.  When she says that it is a good thing Tom killed himself and blames him for the death of 400 men during a strike and for "kicking out" his wife of many years to make way for someone young and pretty, Henry asserts that Tom cannot be judged by ordinary standards.  Henry then relates various scenes from Tom's life.

Their lifelong friendship begins at an old swimming hole when Tom, a boy a few years older than Henry, pulls him into the water against his will to show him how to swim.  Tom purposely loses their subsequent fight, but bests another boy, who starts to battle Henry.  On a dare, Tom dives into the water from a tall tree and gets his hand stuck between two rocks underwater.  Henry is terrified that Tom has drowned and, after he surfaces, Henry spits on a leaf and secures it to Tom's hand with a piece of his own shirt to heal his wound.  The two boys walk home sadly because they know they will be separated soon, as Henry will be starting school away from home, while Tom, whose father is poor, will remain behind.

The resultant scar on Tom's hand is apparent years later at a board meeting of his railroad, when he bangs his fist demanding that the members agree to his purchase of the seemingly insignificant Reno and Santa Clara Railroad.  Because Tom convinced Henry, who had become his secretary, to buy shares in the smaller railroad before word got out about the takeover, Henry was able to make enough money to build the house in which he and his wife now live.

Henry goes on to tell his wife of Tom's courtship of his first wife Sally.  Because Tom, now a trackwalker, cannot read, he brings a letter Henry has written him from business school to Sally, the teacher of the mountain school.  Sally teaches Tom reading, writing and arithmetic and accompanies him on a hot Sunday afternoon for a walk.  At various stopping points up the small mountain, Tom almost proposes, but loses his nerve until they reach the top, where Sally accepts his proposal, despite the fact that her best dress and new tight shoes are now ruined.

Henry then relates to his wife Tom's first meeting with his future second wife, Eve Borden, which occurred after Tom purchased the Santa Clara Railroad, of which Eve's father was president.  Although Tom held a grudge against Borden because he once kept him from joining a club, after spending an afternoon with Eve, a young divorcée, Tom allows Borden to remain president and becomes smitten with Eve.  That night, Tom argues with Sally about their son Tommy, who has been kicked out of college, and leaves to stay at his club for a few days.  Sally had defended Tommy, saying that he should have fun while he is young, unlike Tom, whom she now realizes she had pushed to become a success when he was young and wanted nothing more than to remain a trackwalker.  Henry relates that after they married, Sally, not satisfied with Tom's lack of ambition, and wanting good clothes, a nicer home and a carriage, convinced him to go to engineering school in Chicago while she took over his job as a trackwalker.

Henry now tells his wife that shortly after meeting Eve, Tom tells her that he loves her but that he cannot divorce Sally, and Eve demands that he make up his mind.  Sally, who has noticed a change in Tom, visits him in his office and suggests that they take a trip to Europe together.  She blames herself for becoming a "disagreeable old woman" until Tom confesses that he has fallen in love.  Tom then insists that they take the trip, but Sally, blaming herself for pushing him his whole life, says that he should do what he wants once before he dies.  She walks out of the office in a daze and, after giving her purse to a flower vendor, walks under the wheels of an oncoming streetcar.

Henry tries to explain to his skeptical wife that Tom could not help falling in love.  He relates a scene from twenty-eight years earlier, where Tom comes home to Sally with news that he has been promoted to supervise the building of the Missouri bridge.  Sally then tells him the equally momentous news that she is pregnant.  Overjoyed, Tom says that his boy will be someone to be proud of when he is old.  At Tommy's birth, Tom thanks God.

Soon after Sally's death, Tom marries Eve and invites Tommy to live with them.  During the honeymoon, a strike breaks out, and Tom invades a meeting of his workers.  After telling them that people are depending on his railroad to deliver food, he warns that he has sent for men and guards to keep the trains running.  Violence during the ensuing strike takes the lives of 406 men.

When Henry's wife remains convinced that Tom killed himself because his conscience bothered him over Sally, his treatment of his son and his responsibility for the deaths of the workers, Henry finally reveals what led to Tom's suicide.  Upset at Tom's absence during the six weeks of the labor disturbances, Eve begins an affair with Tommy.  On Tom and Eve's wedding anniversary, he returns home unexpectedly and overhears her on the telephone call someone "darling" and say that her young baby looks like him.  Tom returns to his office in a daze and during a board meeting, keeps remembering Eve's words.  He yells out uncontrollably, and Henry takes him home, where Tom confronts Eve and demands to know whom it is their son looks like.  Tom menacingly approaches the baby, and Eve screams, then agrees to tell, but breaks down and pleads for him not to make her.  Shattered, Tom softly repeats Sally's last words to him, "Why shouldn't you be in love and do as you want just once before you die," then goes into his room after putting his arm around Henry's waist and shoots himself.  He dies in Henry's arms after saying Sally's name.  After Henry finishes telling Tom's story, his wife, without a word, puts her hand on his shoulder and walks upstairs, leaving Henry alone with his thoughts.