Oscar François de Jarjayes is the commander of the French Royal Guards, but even this fearless noblewoman may have met her match. Enter Loulou de la Laurencie, Oscar’s mischievous young niece. Loulou was sent to Oscar's house to improve her manners, but instead finds herself entangled in a bevy of adventures. She quickly becomes the key to helping Oscar and her loyal friends André and Rosalie solve some thrilling mysteries!