This young adult novel is the story of a year in the life of a young Ojibwa girl who, over the cycle of four full seasons, comes to a deeper understanding of life, herself, and the relationship between the two. As it chronicles the year's events, the narrative thematically explores the connection between human beings and nature, the effect of whites on indigenous culture, and the necessity of confronting fear.

A brief prologue describes how a group of canoeing fur traders abandons the sole survivor of a smallpox outbreak, a baby girl, because they're afraid of being infected with the disease that killed everybody else in her Ojibwa community. As he goes, however, one of the traders imagines that if anyone would come back to rescue the girl, it would be his strong-willed, fearless wife Tallow.

Several springs later, seven-year-old Omakayas and her family prepare to move into their summer home, a hand-built birchbark house. After the bark is harvested and the house constructed, Omakayas is sent on an errand to the home of eccentric elder Old Tallow, with whom Omakayas feels an unusual connection. On her way home, Omakayas has an encounter with a family of bears, but after an initial surge of fear and impulsively speaking as respectfully to the mother bear as she would to her grandmother, suddenly feels she's safe. The bears leave, and Omakayas returns home. As the summer progresses, she ponders the meaning of the encounter even as she rejoices at the return of her father from his hunting trip, and has friendly encounters with both a deer and a crow, the latter becoming a family pet.

As summer fades into fall, the family prepares to move from the birchbark house into their cabin in town, harvesting wild rice and other forms of food to get them through the winter. Meanwhile, Omakayas talks with her grandmother about her experience with the bears and discusses her grandmother's use of herbs as medicines. Her grandmother tells her to trust her instincts about both plants and animals. Meanwhile, Omakayas' father and his friends discuss the increasing presence and influence of the white man and consider the possibility of moving west.

Once winter arrives, Omakayas and her family join with the rest of the community to celebrate their coming together once again. Their party is interrupted by the arrival of an exhausted, ill white trader, who is taken into the home of another family. The community is shocked when the man dies in the night, and it is discovered that he had smallpox. Desperate efforts are made to prevent the disease from spreading, but it's too late - several people, including most of Omakayas' family, get sick, and die. Thanks to the intensive efforts of both Omakayas and her grandmother, almost everyone in the family survives, except for Omakayas' beloved baby brother. After his death, Omakayas sinks into depression, reviving only after the intervention of Old Tallow.

The following spring, Omakayas and her family travel into the bush for maple sugaring season. While there, Omakayas has another friendly encounter with the bears, and after healing her other brother, burned by scalding maple syrup, learns that like her grandmother, she has abilities as a healer. Later in the spring, Omakayas is again visited by Old Tallow, who reveals what the reader has suspected all along - that Omakayas is the abandoned girl from the prologue, and that that's the reason she didn't get sick in the smallpox outbreak - . Having survived when her first family was killed, Tallow says, Omakayas was immune the second time it came into her life and was able to give her second family life - to return the favor they did by taking her in and giving her life after she'd been abandoned. After Old Tallow has gone, Omakayas goes into the woods, quietly celebrating her new awareness of her identity and becoming aware that the spirits of her animal friends and her baby brother are with her always.