In this emotionally layered novel of adventure, friendship, and historical and personal discovery, twin sisters diverge on different paths as Gabby seeks to find her purpose while Lucy's purpose is tested. The girls live on Tupper Lake in the New York Adirondack Mountains where their family rents out cabins to canoeists and hikers, and they help run the place. Their personal struggles rise as a mysterious kayaker begins shadowing the cove where they live; a secretive new girl moves to their town; and their father distracts himself by making more and more birdhouses and not being able to sleep. The kayaker turns out to hold a key to their father's past, to the girl, and a life on the fringe in the woods.Amidst these changes, shy Gabby immerses herself in books and her dog, although she yearns for a special talent like others in her family have. While on a hike up newly dedicated Goodman Mountain in Tupper Lake, which her family has connections to, she learns more about civil rights activist Andrew Goodman, who decades ago had spent every summer just a few miles from her. Goodman was murdered in the south, where he went to volunteer for Freedom Summer to help Black people safely exercise their right to vote and have a voice. Inspired by him to help others, Gabby finds courage to bring her dog regularly to the local nursing home and have him interact with lonely residents. When she suffers a big loss, she finds her own voice as well.

Her sister Lucy is a singularly focused swimmer who practices her laps in the lake and at regional swim meets, though failing math has consequences for her swimming. When she finally wins her first meet, a torn bathing suit leads to harassment on social media and she withdraws into herself. Then, sidelined by an injury, she starts opening up to understand the complex truths of herself and those around her: her twin sister, a bully from school, and the new girl, who both her and Gabby befriend.