Secretum tells the story of Jero, a very young bird who lost his mother in a storm. He is then adopted by an adult bird who pretends to love and protect him, but in reality is abusing him. Eventually, Jero grows up and, as a teenager, realizes that his stepmother's caresses are not an expression of true love. He must then summon the courage to escape the painful secret he has been forced to keep for so long.