Jan Arvan

Diego de la Vega, the son of a wealthy landowner, returns from his studies in Spain and discovers that Los Angeles is under the command of Capitan Monastario, a cruel man who relishes in the misuse of his power for personal gain. Knowing that he cannot hope to single-handedly defeat Monastario and his troops, Diego resorts to subterfuge. He adopts the secret identity of Zorro, a sinister figure dressed in black, and rides to fight Monastario's injustice.

When the first manned flight to Venus returns to Earth, the rocket crash-lands in the Mediterranean near a small Italian fishing village. The locals manage to save one of the astronauts Colonel Calder, the mission commander. A young boy also recovers what turns out to be a specimen of an alien creature. Growing at a fantastic rate, it manages to escape and eventually threatens the city of Rome.

When their ocean liner capsizes, a group of passengers struggle to survive and escape.