Poisoned by an oil slick caused by the collision of two ships, a dying seagull named Kengah manages to entrust her egg to a cat named Zorba, making him promise that he will not eat the chick but will care for it and even teach it to fly. Once hatched, the baby seagull is named Fortunata and raised by Zorba with the help of his neighborhood cat friends. For the little bird, who believes she is a cat, the journey of growing up also involves discovering her true nature and accepting how different she is from the companions to whom she has become deeply attached. Meanwhile, danger is lurking in the form of the evil mice led by Big Rat, who have declared war on the feline community with the intention of punishing the group by kidnapping Fortunata and eating her.