Winter, 1539: Mar a de Salinas is dying. Too ill to travel, she writes a letter to her daughter Katherine, the young duchess of Suffolk. A letter telling of her life: a life intertwined with her friend and cousin Catalina of Aragon, the youngest child of Isabel of Castile. It is a letter to help her daughter understand the choices she has made in her life, beginning from the time she keeps her vow to Catalina to share her life of exile in England. Friendship, betrayal, hatred, forgiveness: love wins out in the end.