Loosely based on the 17th century corrido written by José de la Cruz, Adarna follows the journey of Prince Juan and his two older brothers, Princes Pedro and Diego. The King of Berbanya has fallen sick and the only cure for his disease is a song from the legendary Adarna Bird. One by one, the older brothers set off in search for the creature but the years pass by without them returning. Juan then decides to take matters into his own hands and convinces his parents — afraid for their remaining son — to let him go on the same quest.