Since the death of her parents in a car accident, Vanessa's relationship with her grandmother splintered into a cantankerous silence. Along with her two kids - Maeve, a spunky 10-year-old, and Brodie, an inquisitive 7-year-old - Vanessa visits her Grammy Francis to interview her about the family history. Inside a secret passage in her 140-year-old home, Maeve and Brodie discover an old ship captain's box, and inside they find a handwritten manuscript bound with a deerskin map.

As the children read the manuscript with their mother and great-grandmother, they are taken back to 1848. There they meet their great-great-great-grandmother Claire, who, while riding her horse in the forest outside of Boston, has a chance meeting with Daniel Benet, who she slaps because she can. Both are mysteriously awestruck by one another. Five months later, with their meeting in the forest still silently lingering on their hearts, a twist of fate finds the two heading to San Francisco on the SS California with Daniel's new friend and business partner Philippe and Claire's new husband Ashley.

In their journeys, they meet Chang Hui, a Chinese doctor and Moon Bear, a young Maidu shaman and together they face emotional and physical challenges that contour and define them as individuals and friends. Together, they weave the tapestry of Claire's adventure for Maeve, Brodie, and their mother Vanessa, who must confront their own yearnings for family, acceptance, and the fate of the mysterious hidden family secret of the ship captain's box that will change them forever.