The orphan Catherine Maguet, nicknamed "La grande Maguet", was taken in by a young and good chatelaine, Suzanne de Norvaisis. Edmond, the husband of the latter, during a trip abroad, falls madly in love with another and will go, to conquer this one, to poison his wife. Imprisoned then released, the lord will finally marry the one for whom he has become a criminal. But the great Maguet will avenge her beloved murdered benefactress...