Fifteen-year-old Sadie knows there's something wrong with her sister Annika. It's like a monster has taken over her sister's mind, making her volatile and moody, and Sadie has no idea how to help. When Annika runs away from home, Sadie is forced to stay at her grandpa's cottage while her parents search. Sadie feels useless, truly unable to save her sister from afar. She begins tending her grandfather's garden and discovers a rare hummingbird that is facing its own impossible challenge--losing its habitat. Sadie befriends a boy next door who helps her work through her guilt over Annika's disappearance and focus on what she can control. As Sadie tends to the garden and creates a safe space for her beloved hummingbird, she gains calm and clarity. But her sister's return threatens to upend the peace she has sown.