In the village of Kilburne, Scotland, twenty-six-year-old Maggie Wylie lives a spinster's life with her two bachelor brothers, James and David, and her widowed father Alick. One evening, after a town political meeting at which David is shouted down by John Shand, a poor but ambitious train station porter, the Wylies pretend to go to bed in order to catch an intruder who has been sneaking regularly into their home. To their surprise, the intruder turns out to be John, whose intention is not to steal from the Wylies, but to read the books in their parlor. Desperate to see their bright but plain sister married, James and David propose a plan to the somber young scholar: if the Wylies contribute £300 to John's education, he must marry Maggie in five years if she is still single. In spite of Maggie's age, the twenty-one-year-old John agrees to the deal, and a formal contract is signed. Five years later, as the now-educated John is preparing to fulfill his end of the bargain, he is asked to run for Parliament against an aristocratic incumbent. Out of respect to Maggie, John refuses the invitation, but Maggie, who has genuinely fallen in love with her fiancé, convinces him that their marriage can be postponed until after the election. After a difficult campaign, John wins the election, and he and Maggie marry and move to London. Soon after, John is befriended by Lady Sybil Tenterden, the attractive daughter of a Scottish party leader, who schools the lowborn Scot in aristocratic manners. Then while Maggie, who magnanimously had offered John a chance to back out of their deal, quietly helps her husband's political career, John begins an affair with Sybil. When Maggie discovers John and Sybil together one day, she nobly offers to grant a divorce but suggests that, before John resigns his Parliament seat, he go to the country for a month to finish his book on the British gold standard. Maggie also arranges for Sybil to join John in the country, while she secretly goes to see Charles Venables, John's party's leader. Using the resignation letter that John had written in regards to his divorce, Maggie convinces Venables that John actually is resigning in protest of the country's stagnant economic policies. After John then is hailed as a political hero and is promised an important new post, Sybil admits to John that she has grown tired of their affair. Quietly relieved by Sybil's confession, John returns to his London home and is overjoyed to find Maggie waiting for him. After Maggie reveals to John that "what every woman knows" is that the success of men depends on the secret manipulations of their women, she cajoles her husband to laugh for the first time in his life.