Le cheval de Dorothée

Plot
Official summary translated from French:

"Where is Merlin, Dorothy's beloved horse? Ever since he disappeared, the girl is heartbroken. She helps Cerise, her best friend, to prepare for her Amazon competition, but she has a hard time relaxing... Could Athena, the magic mare, help her find her lost horse?"

Characters

 * Athena
 * Cerise
 * Dorothy
 * Merlin