Mare Nostrum (Our Sea)

Captain Ulysses Ferragut, the last of a famous Spanish family of seafaring fame, meets Freya Talberg, a beautiful and ruthless German spy, in Pompeii and falls in love with her. Freya's superiors plan to use Ulysses' knowledge of the Mediterranean to assist them in supplying their submarines with fuel, using Freya as bait. Later, Ulysses returns to Naples to find Freya and her spy ring departed, and he learns that his son Esteban, whom he idolizes, has been killed on a torpedoed liner. Seeking revenge for the death of his son and his own mistakes, he turns his ship, the Mare Nostrum, over to the French and volunteers as commander. Freya, disheartened by the results of her work, sends for Ulysses, but the memory of Esteban causes him to cast her off, and she is executed by the French for espionage. Ulysses' ship is torpedoed; and though he sinks, his attacker is itself swallowed up by the sea.