Lydia. daughter of the younger branch of the ancient family of Louzat, on her eighteenth birthday is in the garden. A man steps out of the bushes and hands her a message, telling mysteriously of a super-important secret hidden in an unnamed massive volume bearing her family’s ancestral arms. Count Gerard, her uncle, feigns to pay no heed to the communication but secretly searches in the library. Failing, he decides that in the majestic castle of the senior branch of the family, with whom he is at enmity, he must seek. Using as an excuse for Gerard’s call the introduction of his beautiful niece, Count Jules receives them courteously. The latter finds that his interest in his sweet kinswoman melts the rancor of the years. Returning from the garden with her, they confront Count Gerard in futile and furious quest. Gerard slinks away under Jules’ fiery denunciation. Lydia evinces sympathy for Jules. To get her out of his way, Gerard sends her to convent confinement. Here fate blindly leads to the solving of the secret. She is apprehended and her guardians, informing Gerard, lock her in her room, unknowing that in the struggle Lydia had torn from the page the few lines whose knowledge would have saved Gerard his life, when, with masked accomplices, he attacks Jules in his castle and finds in the subterranean shrine a treasure enormous. How by deft trick and adroit scheming Lydia wins her way to liberty, arriving in time to revive her Jules from the unconsciousness of brutal blows; how they found Gerard and his man buried under the avalanche of jewels and gold; how love joined the rival families forms a motion picture of thrilling throbs and tender charm.