Little rat at the Opera de Paris , Delphine ( Delphine Desyeux ) is ecstatic. At twelve, she has been chosen to play the role of Galatea in the next ballet prepares the Palais Garnier . One evening, a small group of dancers , defying prohibitions, ventures into the roof of the Opera . But jealousy, one of the girls closed the door locked, preventing Delphine back ... This great adventure aired for the first time in 1966 on television was written by Odette Joyeux , from his own experience little rat when she was not an actress. By the famous cinematographer Philippe Agostini , the series goes behind the scenes of the ruthless world of dance . The adorable Delphine Desyeux , which will star opposite Jacques Brel in 1967 in the unforgettable " The Hazards of the trade" , is surrounded by Odette Joyeux , Louis Velle , Pierre Mondy , Françoise Rosay but also real dancers of the Opera in their own roles.