Heidi, a spirited five-year-old orphan, enters the care of her aunt Dete following her parents Tobias and Adelaide’s deaths. At five, Dete brings her to the secluded Alm-Onji, her grandfather, a figure shrouded in village rumors of past violence. Undeterred by his gruff exterior, Heidi’s infectious curiosity and warmth slowly thaw his guarded heart, forging an unshakable bond.

Embracing life in the Swiss Alps, she befriends Peter, a young goatherd, and his blind grandmother, sharing days herding goats and wandering meadows. Though content, her grandfather’s isolation denies her schooling, leaving her unable to read—until Dete reappears three years later, luring Heidi to Frankfurt as a companion for Clara Sesemann, a wheelchair-bound girl from a wealthy family.

In Frankfurt’s rigid household, Heidi’s untamed spirit clashes with governess Miss Rottenmeier’s strict routines. She bonds with Clara and, under her grandmother’s mentorship, discovers the joy of literacy. Yet crushing homesickness triggers sleepwalking episodes, mistaken for supernatural hauntings. A physician deems her condition dire, compelling her return to the Alps.

Reunited with the mountains, Heidi’s radiant vitality reignites. Her newfound literacy inspires Alm-Onji to renovate their village home, enabling her education. His efforts bridge the rift with villagers, ending years of estrangement. When Clara visits, Heidi and Peter guide her through alpine therapies, culminating in Clara’s miraculous first steps.

Heidi’s unwavering optimism and resilience anchor her journey, catalyzing profound change in others while remaining true to herself. Initial designs depicted her with pigtails, later revised to short, windswept hair reflecting Swiss children’s practicality. Media adaptations, like the 1979 film and 1996 OVAs, re-edit original narratives without altering her core story.