Nathan Juran	...	(Director)
Robert Creighton Williams, Christopher Knopf	...	(Writer)
William Hopper	...	Col. Robert Calder
Joan Taylor	...	Marisa Leonardo
Frank Puglia	...	Dr. Leonardo
John Zaremba	...	Dr. Judson Uhl
Thomas Browne Henry	...	Maj. Gen. A.D. McIntosh
Tito Vuolo	...	Commissario Unte
Jan Arvan	...	Signore Contino - Government Official
Arthur Space	...	Dr. Sharman
Bart Braverman	...	Pepe

Summary: The first spaceship to visit Venus crash lands in the sea, freeing a small native Venusian creature called the Ymir. Eventually growing to enormous size, it threatens the city of Rome.