Maria Rainer, Kara Tointon Rainer, a postulant at Nonnberg Abbey in Salzburg, spends a quiet day contemplating life high in the mountains. When she returns to the abbey, she is told by the Mother Abbess that she is to become the new governess for the von Trapp children. Arriving at the von Trapp home, Captain von Trapp greets her with cool reserve, and the children march in with military precision. Maria soon learns that the Captain has emotionally shut himself off since the death of his wife, and she decides to win the children over by teaching them to sing, hoping music will open their hearts and earn the family’s trust.
A month later, the Captain returns home with Elsa Schraeder, whom he is courting, and their friend Max Detweiler, who is hunting for the perfect local singing group for the annual Kaltzberg Festival. When the children arrive in play clothes—sewn from fabric Maria had salvaged from her old bedroom—Captain von Trapp is furious and embarrassed by the sight. Maria bravely tells him that he does not truly know or understand his children, and that they need him, but her words only wound him further, and he orders her to return to Nonnberg Abbey. Yet, when he later hears the children sing for Schraeder, his eyes are opened to the truth Maria has been trying to show him, and he reunites with his brood, asking Maria to stay on as governess.
The Captain hosts a grand party to introduce Schraeder, and when the band plays the Ländler, his youngest child asks Maria to teach the dance, with the Captain stepping in to assist. As they dance, a quiet attraction blooms between Maria and the Captain, though Maria tries to hold back. Brigitta, one of the Captain’s daughters, confronts Maria about the growing tension, confirming the unspoken truth. Schraeder finally gathers the children to say goodnight to the guests, and Max is instantly taken with the idea of having the children perform at the festival.
Later, Maria slips away to the Abbey and confides in the Mother Abbess that she has fallen in love with the Captain and is ready to take her vows of poverty, obedience, and chastity. The Mother Abbess gently discourages but encourages her to pursue the life she was meant to lead. Maria returns to the von Trapp household, where she is warmly welcomed by the children, who have missed their musical joy since her departure. Yet she learns that the Captain intends to marry Schraeder, and she resolves to fulfill her duties until a replacement can be arranged.
Ultimately, the political differences between Schraeder and the Captain reveal that they have no future together, and Schraeder leaves. In the meantime, the Captain and Maria acknowledge their feelings for one another and decide to marry at the Abbey. While on their honeymoon, Germany annexes Austria, a turning point that forces them into action. On their return, the Captain is ordered to accept a commission in the German Navy and report to Bremerhaven. Maria, quick on her feet, presents the Admiral in charge with the program for the Kaltzberg Festival, demonstrating that the von Trapp Family Singers are booked to perform, effectively buying time. They are granted permission to perform, and a final concert becomes a pivotal moment: Max announces that a guard of honor will escort the Captain away as soon as the concert ends. Maria leads the family in one last song, and, one by one, they slip away to the Abbey. Nazi soldiers scour the area, but the family vanishes, fleeing Austria over the mountains with Maria’s help, choosing liberty and song over fear.
