Salzburg, Austria, 1938, on the eve of the Anschluss. In the cloistered sanctuary of Nonnberg Abbey, the nuns invoke Psalm 110 and sing songs of praise (“Preludium”). However, one of the postulants is nowhere to be found: Maria is instead out in the hills, where she goes “when her heart is lonely,” singing at the top of her voice (“The Sound of Music”). Sister Berthe, Sister Sophia and Sister Margaretta debate with the Mother Abbess as to whether Maria is truly ready for a life of obedience and humility (“Maria”). The Mother Abbess calls for Maria, and they discover a shared love of one particular childhood song (“My Favourite Things”).
To help Maria mature before committing to the religious life, the Mother Abbess sends her out from the Abbey to become a temporary governess to the seven children of a former naval officer, Captain George von Trapp. Upon arriving at the von Trapp home, Maria realises that he Captain has, since the death of his wife, emotionally closed himself off. The children march; they do not play. Furthermore, they have grown up without music in their lives. Maria understands that the way to gain their trust and acceptance is by teaching them the basics of singing (“Do-Re-Mi”).
That evening, the oldest child, Liesl, steals away to meet Rolf, a local boy who’s caught up in the political fervor of the streets. He warns her of the dangers of her innocence and offers himself as a suitable protector. She in her way, accepts (“Sixteen Going On Seventeen”). Meanwhile, a loud thunderstorm causes the frightened children to seek out Maria in her bedroom, where she diverts their fears with a rousing folk song (“The Lonely Goatherd”).
The Captain returns a month later with Elsa Schraeder, a sophisticated Viennese widow. They are accompanied by Max Detweiler, Third Secretary in the Ministry of Education and Culture, who is on the hunt for the perfect local singing group to perform at the annual Kaltzberg Festival. Elsa finds it charming here in the provinces, but is frustrated that the Captain has yet to propose to her. Max explains what’s standing in the way: both she and the Captain are rich! (“How Can Love Survive?”).
Maria arrives with the children, all wearing clothing that Maria has made from the old curtains in her bedroom. The Captain is embarrassed and enraged. Maria confronts him and tells him how little he understands his children, and he orders her back to Nonnberg. But when he hears the children singing for Elsa (Reprise: “The Sound of Music”), his heart opens up as he realises what Maria has done in bringing music back into his home. He asks Maria to stay.
The Captain throws a lavish party so that the local gentry can meet Elsa (“The Grand Waltz”). However, the political divide is widening between those that support the proposed German takeover and those, like von Trapp, who believe in Austrian sovereignty. As the orchestra plays an Austrian Folk dance (“Ländler”), young Kurt tries to teach it to Maria. The Captain steps in, and as their arms intertwine, the Captain and Maria realise an unspoken attraction between them. Maria breaks away. Meanwhile, Elsa has asked the children to sing for the guests (“So Long, Farewell”). Max is thrilled: a singing group of seven children in one family? Perfect for the Festival! The children make their way to bed; the guests make their way to dinner; and Maria, confused by her encounter with the Captain, leaves without saying goodbye and flees back to Nonnberg Abbey. There she tells the Mother Abbess that she is ready to take the orders of poverty, obedience and chastity. But the Mother Abbess sees that Maria has fallen in love and encourages her to see her way forward and face her problems: to find the life she was born to live (“Climb Ev’ry Mountain”).
Max, in anticipation of the upcoming Kaltzberg Festival, rehearses with the children. But without Maria, they’ve lost the joy of music-making. Suddenly, Maria returns and they’re delighted! But they have news for her: Father is going to be married. To Frau Schraeder. Maria’s heart is broken, but she resolves to see her duties through until arrangements can be made for a new governess.
The political situation is worsening, and Max and Elsa are imploring the Captain to weather the coming storm by being noncommittal (“No Way To Stop It”). But the Captain is unwavering in his disgust for the Nazis, and he and Elsa realise that they cannot share a future. Elsa returns to Vienna for good. Seeing Maria again, the Captain now understands what he and Maria have both known deep inside for many weeks (“Something Good”).
The Nuns of Nonnberg Abbey celebrate the wedding of Maria Rainer and George von Trapp (“Processional & Maria: The Wedding”). But while Maria and the Captain are away on their honeymoon, the Anschluss occurs and Germany and Austria are now united. The Von Trapp house is the only one in the province not flying the flag of the Third Reich (“You mean the flag with the black spider on it?” asks Brigitta). Georg and Maria hurry back to find that much has changed: many have joined ranks with the Nazis, including Rolf, and even Franz the butler. Max, against the Captain’s wishes, has been readying the children for their performance at the Festival. The Captain is steadfast in his refusal to allow his family to perform on behalf of an Austria which no longer exists, and Maria stands by him. Liesl now sees how much Maria truly loves the Captain, and Maria shares her new understanding of how to spend one’s love (“Reprise: Sixteen Going on Seventeen”).
Admiral von Schreiber of the Navy of the Third Reich, accompanied by Herr Zeller, the local Nazi leader, arrives to inform von Trapp that he must accept a commission in the German Navy and report immediately to Bremerhaven. Thinking quickly, Maria displays the program for the Festival showing that the Trapp Family Singers – which includes the Captain, of course, as head of the family – are scheduled to perform, so he couldn’t possibly leave now. Admiral von Schreiber comprehends the situation and grants permission for the Captain to report to duty several days later.
The Festival beings (“Reprise: Do-Re-Mi”) and von Trapp himself sings a quietly defiant hymn to his beloved Austria (“Edelweiss”). But when Max announces that a guard of honour is waiting to escort the Captain away as soon as the concert is over, Maria leads the Von Trapp family in more song as they escape, one by one, into the night (“Reprise: So Long, Farewell”). Max gives out the concert prizes slowly, buying time. The Trapp Family Singers are announced as winners of the Festival, but they are nowhere to be found.
The family takes refuge in the garden of Nonnberg Abbey as Nazi soldiers swarm the hallowed ground. It is Rolf who discovers the von Trapps, but seeing Liesl, he chooses not to reveal their hiding place. Still there seems to be no way out for the von Trapps: the Nazis have closed the border and are guarding every road. The family has no choice but to make their way to freedom by way of the mountain. It is a daunting journey, but Maria, who grew up on that mountain, knows the way. And the Mother Abbess reminds them that they will have help: “For ye shall go out with joy and the very hills shall break forth before you into singing” (“Finale Ultimo: Climb Ev’ry Mountain”).