Harry Melville Quincy lives with his two sisters, Lettie and Hester, in their New Hampshire home, the last remnant of a family fortune lost in the Great Depression. Harry, a mild-mannered designer at the Warren Mill, is affectionately known as "Uncle Harry" by both young and old. One day, Deborah Brown, a beautiful young woman from the Mill's New York office, arrives in town, and Harry quickly attracts her attention. After a few weeks, the two become a couple and Deborah decides to move to New Hampshire. Three months later, Deborah tells Harry that she has been invited on a European trip by their boss, John Warren, prompting a jealous Harry to propose. While Hester is delighted by Harry's engagement, her younger sister Lettie plots to break up the couple. After six months, Harry and Deborah remain unmarried, as Lettie has rejected all alternative housing that would allow the couple to wed and move into the family home. Realizing that the only way to break free of his sisters is to leave town, Harry and Deborah decide to elope and move to New York. Lettie, however, feigns a sudden illness and is rushed to the hospital. Recognizing the ruse, Deborah insists that Harry decide once and for all between Lettie and herself, but thinking that his sister is in mortal danger, Harry refuses to leave town. Deborah then breaks their engagement, and three weeks later, the Quincys are informed that Deborah and John have married in New York. An elated Lettie rises from her sick bed in celebration, only to be denounced in Harry's presence by an angry Hester. Finally realizing what a fool he has been, Harry decides to poison Lettie, but Hester is mistakenly given the drugged cocoa and dies. Lettie is later tried and convicted of her sister's murder and sentenced to the gallows. While his sister awaits the hangman, Harry's conscience begins to get the better of him and he confesses to the crime. No one, however, believes that the virtuous Harry would commit such a horrible act. Even the vengeful Lettie refuses to support his claim, knowing the years of tortured guilt he will endure after her execution. A dreaming Harry is then awakened by Deborah, who has decided not to marry John and has returned to him. As the couple prepares to elope, Hester enters the room, offering them her congratulations, as well as receiving Harry's farewell message for the bed-ridden Lettie.