An unlikely shipboard romance occurs in 1840 between a wealthy young Mormon convert from England, Mary Rose Ashley, traveling with her family from England to America, and Gabriel MacKay, one of the builders and designers of the new Cunard line who is evaluating the clipper ship's performance. Married on board, the newlyweds make their way to the new Mormon settlement in Nauvoo, Illinois and are just settling in when Prophet Joseph Smith receives a revelation from God about polygamy. As one of their close friends from the voyage is suddenly widowed during anti-Mormon riots, Gabriel announces he will marry the beautiful Bronwyn and raise her baby as his own.Mary Rose loves Bronwyn like a sister, but cannot imagine sharing her husband. Assuming that the relationship will remain platonic, she agrees, and Bronwyn and Mary Rose begin to come to terms with what plural marriage truly entails. Is this really what God wants for them?