Adapted from a play by James Barrie, a school-teacher pretends to be her own niece to win her old beau after he returns from the Napoleonic wars.
In 1805 England Susan Throssel (Fay Bainter) tells Mary Willoughby (Estelle Winwood) that they are old maids. Phoebe Throssel (Katharine Hepburn) turns the recruiting sergeant (Eric Blore) out of the house. Phoebe tells Susan how she met Valentine Brown (Franchot Tone), and Susan offers her the wedding gown she never wore. Valentine calls on Phoebe and Susan, who leaves them alone. Valentine tells Phoebe he enlisted and says good-bye, laughing at the mention of marriage. Valentine marches off to war for ten years.
Phoebe and Susan teach school, and soldiers return from the war. Phoebe tells Susan not to fear the big boys. Captain Valentine Brown comes in and greets Susan, while a boy chases Phoebe. Valentine sees Phoebe has changed and does not invite her to the ball. Phoebe tells Susan that she regrets she is thirty. The maid Patty (Cora Witherspoon) is ten years older but is still hopeful. Phoebe pretends she is her niece Livvy, and Valentine invites her and Susan to the ball, where he finds Livvy dancing with a lieutenant. At croquet Valentine wins the field and retreats with Livvy in the rain. Valentine goes off to see Phoebe, and Livvy runs home. Valentine visits Phoebe in bed. Phoebe tells Susan that when Valentine proposes to Livvy, she will say he is too old. At a ball Valentine dances with Livvy, and Patty meets the sergeant to warn Phoebe the Willoughbys are coming. Susan interrupts Valentine to warn Livvy. Phoebe greets Mary and sends Valentine off again. Mary, Henrietta Willoughby (Florence Lake) and Fanny Willoughby (Helena Grant) realize that Phoebe is Livvy. Valentine tells Livvy that she will find someone and that he loves Phoebe. Livvy tells Valentine that Phoebe loves him. Livvy and Valentine quarrel, and he leaves.
Mary calls on Livvy, but Susan and Phoebe say she is ill. Valentine calls on Phoebe and asks to take care of her. Henrietta and Fanny come in. Valentine says he loves Phoebe, not Livvy. Valentine learns the truth but plays along, making the Willoughbys leave. Valentine asks Phoebe to produce Livvy and asks Patty why the trick is being played. Livvy pretends to be sick, and Susan tells Valentine that the Willoughbys watch the house. So Valentine takes out a bundle dressed as Livvy and sends the sergeant and Patty off to bury Livvy. Valentine tells Susan to burn the school sign and asks Phoebe to marry him. Phoebe accepts, and they kiss.
This refined comedy takes on the prevalent fear in this era that a young woman might end up an old maid if she is not careful.