Heidi (Emma Bolger) is an orphan who is now supposed to live with her grandfather (Max von Sydow) in the mountains. At first, the grandfather has little desire to take care of the little girl. But over time, the two get to know each other and develop a close bond. The following summer, Heidi's aunt is coming to take her back to the city. Heidi does not want to go with her, and her grandfather is not willing to give up his newfound “family” either. But the aunt is adamant, because she has promised a rich acquaintance that Heidi will be the new playmate of her sick little daughter Clara. Once they arrive in the city, the girl from the mountains adapts to the new situation, despite the strict regime of the housekeeper, Miss Rottenmeier (Geraldine Chaplin). But after a few months, Heidi becomes homesick for the mountains and her grandfather. On the doctor's orders, she is sent back to the mountains. The grandfather is still deeply affected by the loss of his granddaughter and recovers only slowly after her return. When a letter arrives from Clara, Heidi is overjoyed – because she will also spend the summer in the mountains with her entire family. Heidi feels that she can finally unite her two families...