The play is set in Bulgaria and set during the brief Bulgarian-Serbian war in the 1880s. It opens with the young romantic Raina Petkoff and her mother Catherine talking excitedly about a successful cavalry charge led by the handsome and heroic Sergius, to whom Raina is betrothed. They are thrilled at his success. Their defiant young servant Louka comes in and tells them that there will be fighting in the streets soon, and that they should lock all of their windows.
Raina’s shutters do not lock, and shortly after the gunshots start that night, she hears a man climb onto her balcony and into her room. He is a Swiss professional soldier fighting for Servia. Though he fights for the enemy and is not in the least heroic (he fears for his life, threatens to cry, and carries chocolates instead of ammo) Raina is touched by his plight. He angers her when he tells her that the man who led the cavalry charge against them only succeeded because he got extremely lucky—the Servians were not equipped with the right ammo. Raina indignantly says that that commander is her betrothed, and the man apologizes, holding back laughter. Raina nevertheless agrees to keep the man safe, saying that her family is one of the most powerful and wealthy in Bulgaria, and that his safety will be ensured as their guest. She goes to get her mother and when they return he has fallen asleep on Raina’s bed.
In the next act the war has ended, and Major Petkoff (Raina’s father) arrives home, and Sergius and Raina are reunited. They speak lovingly to one another about how perfect their romance is. But when Raina goes inside, Sergius holds Louka in his arms, clearly lusting after her. Louka believes he is taking advantage of her because she is a servant, and tells him she does not believe she and he are any different simply because he is rich and she is poor. They part just as Raina returns. Then, to make things more complicated, the man from Raina’s balcony, announcing himself as Captain Bluntschli, arrives, to return a coat he was loaned the morning after he rested at the house. Catherine tries to keep him from being seen, but Major Petkoff recognizes him, and invites him inside to help with some of the last remaining military orders.
In the final act, in the library, it comes out that Louka, though she had been assumed to be engaged to the head servant Nicola, is in love with Sergius, and he is in love with her. Raina eventually admits she has fallen for Bluntschli, who is at first hesitant, believing her to be much younger than she is. When he finds out her real age (23 rather than the 17 he had thought she was), he declares his affection for her. The play ends happily, with two new couples.
