Yael and Sheffi are best friends. They have invented secret names for one another (Yael is Luli, Sheffi is Diego), and they share a passion for all things secret. They also share a common secret wish: to have their own horse, and they begin devising ways to save enough money to buy one. One day, they follow a wagon carrying a beautiful brown horse to a house surrounded by a wall nearby, and thus begins their adventure.
The house, they soon discover, belongs to Saar and his sister, Rama, who own a farm where they look after several horses, including their own - Pegasus and Diana. Yael and Sheffi gradually befriend the owners, as well as the two horses, and are determined to discover the secret behind their names. As they learn to look after the horses, they also learn Saar's sad secret - why he sits in a wheelchair, and why he calls himself Bellerophon.
With the help of Yael's grandfather, Amikam, the girls learn that the horses' names, as well as Saar's nickname, come from Greek mythology. And with these answers, they are able to make sense of Saar's condition.
Unable to ride competitively as he once did with great talent and success, Saar realizes he must give Pegasus away so that he can fulfill his potential. Yael, devastated, steers clear of the farm, the horses and the people she has become attached to, and becomes estranged from her best friend. But late one night, she receives a phone call telling her that Diana is about to deliver a pony. This extraordinary experience, and the new pony, lift her spirits, giving her the greatest gift of all.