Heidi's Song tells the story of orphaned Heidi, who is sent by her strict aunt to live with her reclusive grandfather in the Swiss Alps countryside.
She quickly adapts to her new home and brings joy to her grandpa, the animals, and everyone else there.
Heidi also meets a kind sheepherder boy and forms a friendship with him.
However, her aunt returns and takes her to the city to work as a servant for a wealthy family with a sad, handicapped daughter named Klara.
Heidi befriends Klara and finds ways to make her happy, but Klara's strict parents disapprove of Heidi's actions and punish her.
They lock Heidi in a basement where an evil rat lives.
Heidi's friends from the countryside, along with Klara, come to her rescue and help her return to her beloved grandfather.