Adapted from J. M. Barrie's play, a family helps educate a young man so that he will marry their sister, who helps him in his political career.
James Wylie (Dudley Digges) and his father Alick Wylie (David Torrence) buy a watch to console unmarried Maggie Wylie (Helen Hayes). Her brother David Wylie (Donald Crisp) speaks at a meeting, but John Shand (Brian Aherne) criticizes him and is jeered. The Wylies wait up to catch a burglar. John sneaks in, turns on a lamp, and reads a book. They let him study and decide to offer him 300 pounds for his education provided he will marry Maggie after five years if she is still single and wants him. John objects, and they discuss it before he and Maggie agree.
Five years later they plan the wedding. Maggie plays piano, and they sing, "Loch Lomond." Men come in and urge John to stand again for Parliament. John says no because of his new responsibility. Maggie urges him to run, and he agrees. John campaigns, and Maggie helps his speech. John is elected. Maggie shows she can speak French to the Contessa (Lucile Watson). John speaks to her niece Sybil (Madge Evans), who invites him to London. Maggie says Sybil is beautiful; but John says he will hurry the wedding because she waited. Maggie says she won't give him up even though she knows he could do better now. John gets off the train and makes a speech that he is marrying Maggie, who says, "My constituents!"
Sybil invites John to her flat, but he says it is not proper. The Contessa advises Maggie to help John. He has written on finance and suggests going off the gold standard. Venables (Henry Stephenson) comes in and sees the Contessa after nineteen years. Maggie tells him that John will put the country above his party, making Venables happy. John asks Sybil if they could declare their love openly. Maggie sees John give Sybil a jewel. Maggie invites Sybil to stay for tea with her visiting family, who give Maggie a shawl for her second anniversary. Maggie says that John gave her a pendant and gets it from Sybil; but John says he gave it to Sybil. Maggie says she knew and asks her brothers to go upstairs. Maggie talks to John and Sybil. John wants to leave, but scandal would end his career. Maggie calls the Contessa so that John can visit her with Sybil there too. Maggie visits Venable and shows him John's letter of resignation for a principle. Maggie visits the Contessa and says goodbye to John. Maggie says she hoped that John would tire of Sybil. Venables welcomes John back and says he will get a better position. Sybil asks John if he wants to go back to Maggie. Sybil is tired of John and says goodbye. John goes home and tells Maggie that she made him a great man. She says every woman knows the power behind men, and she gets him to laugh at himself.
Scottish morals and values are depicted in this domestic and political drama. A woman who knows that others are prettier and more charming uses her intelligence to help the man she loves get what he wants and become a success.