The novel focuses on
Constantina, Princess of Portugal;
Dom Pedro, Prince of Portugal and Constantina's husband; and
Agnes de Castro, who is Constantina's loving and loyal friend. Pedro secretly adores Agnes, but Elvira (who is in love with Pedro herself) reveals this to Constantina. Meanwhile, Don Alvaro (the brother of Elvira) tries to secure Agnes's affections. Agnes tries to leave
Coimbra, but Constantina and Pedro convince her to stay. Constantina, Pedro and Agnes try to preserve their friendship and love for each other, but struggle with their divided affections. Constantina dies of grief. Alvaro, following King
Afonso's advice, kidnaps Agnes. After her death, Pedro takes his revenge by embarking on a war against his father. ==Reception==