A concert violinist becomes charmed with his daughter's talented piano teacher. When he invites her to go on tour with him, they make beautiful music away from the concert hall as well. He soon leaves his wife so the two can go off together.
After a successful tour ended in New York, the famous violinist Holger Brandt returns to his home in Stockholm. In the birthday party of his beloved daughter Ann Marie, he feels attracted by and plays with her piano teacher, Anita Hoffman, who is waiting for a music scholarship in Paris. They incidentally meet each other in a concert, have a drink together and begin a love affair. Holger leaves his family and travels with Anita in a tour, and later they spend vacation together. But Anita earns the expected scholarship and travels to Paris, and Holger decides to visit Ann Marie. A car accident changes the destiny of the Brandt family.
- Renowned violinist Holger Brandt (Leslie Howard) finishes the final concert of his tour to ardent applause. He informs the fervid New York audience that this was the last performance of his accompanist, friend and mentor, Thomas Stenborg (John Halliday), who will now retire from touring. Holger himself will embark upon another tour after a few months' rest. He is in search of a new accompanist.
Holger and Thomas return to Stockholm, where they are fondly welcomed by their respective spouses. Holger's wife, Margit (Edna Best), has been bringing up their two children, Eric (Douglas Scott) and Ann-Marie (Ann E. Todd), on her own for the past few years. Eric is now a teenager, while Ann-Marie is six. Ann-Marie has become a gifted pianist in Holger's absence under the tutelage of Miss Anita Hoffman (Ingrid Bergman), a young musician of exceptional promise. Anita is Thomas's prized pupil and is studying towards the prestigious Jenny Lind scholarship offered by a music academy in Paris.
Holger is at first uninterested in Anita. However, he is forced to notice her when she plays the piano brilliantly at Ann-Marie's birthday party. Holger joins her on his violin and is stunned by their electrifying synchrony. He offers her to be his accompanist on tour but she declines, citing her need to study for the scholarship.
Holger and Anita gradually fall in love. Initially, Anita feels guilty about the affair and attempts to break off her relationship with Holger by leaving Stockholm. However, Holger confesses his true feelings about Anita to Margit. This results in a separation which leaves him free to commence the next tour with Anita as his accompanist.
Holger and Anita perform together to immense acclaim. At the end of the tour, they go on vacation to a picturesque seaside town in France. Anita receives a letter from her former mentor, Thomas, informing her that she has won the Jenny Lind scholarship. However, she burns the letter rather than allow her career to stand in the way of her relationship with Holger. Holger is deeply in love with Anita but she notices that he occasionally longs for the family he has left behind. He befriends a little girl named Marianne (Maria Flynn), who reminds him of his daughter Ann-Marie.
Thomas Stenborg visits the couple as their mutual friend. He informs Holger that Margit is seeking divorce and urges him to sign the papers immediately to enable both of them to move on. Holger is reluctant to take this final step to uproot himself from the past. Thomas also speaks to Anita separately. He expresses his disappointment that she is neglecting her promising career and asks if she truly believes that Holger can forget his family. Anita sadly realises that she and Holger cannot build a life together based on the unhappiness of others. She has been no more than an "intermezzo" in his life. She leaves the next day, presumably to Paris to accept her scholarship, leaving a letter to Holger that urges him to return home.
Holger is devastated but is too proud to return to Stockholm now that Anita has left him. He finally decides to return for a day when he learns that Thomas has promised Ann-Marie that her father will return by spring. Knowing that Ann-Marie wants a camera, Holger buys a camera for her as a present and goes to visit her at school. Ann-Marie is so delighted to see her father across the street that she runs into the middle of the road and is hit by a cab. Holger rushes her home to Margit and sits awake in the drawing room overnight while the doctor and Margit tend to Ann-Marie in an upstairs room. He reconciles with his son, Eric, after admitting to Eric that he has erred gravely and asking for his forgiveness.
The next morning, the doctor informs a haggard-looking Holger that his daughter will make a full recovery with time and rest. Holger is immensely relieved but believing that he has lost his place in the family, makes for the door. Before he can leave, Margit calls out to him and welcomes him home. Holger turns around towards her and closes the door behind him as he walks back into their home.