The Ultimate Eve

Her creators had no doubt of her effectiveness. She would conquer this planet ... the armed might of Earth would vanish before her.
The sun had not yet taken the chill out of the early April morning that broke on the foothills of the Rocky Mountains, when the ship settled to the ground. It was surprisingly large compared to the aircraft native to this planet, and yet ridiculously small to have brought enough men and material to launch an invasion across light years of space.
The landing went unobserved in this fearful year of 1955. The world faced too many crucial crises of their own making to consider the necessity to be watchful for an extra-terrestrial invasion.
Hardly had the craft come to rest, when the outer lock slid noiselessly open and a small ladder-like stairway came down until it too had touched earth.
A man appeared in the doorway, pausing to study the landscape which lay before him. His features, his body, were human. Despite his being too well muscled, and his face unusually handsome, he would never have aroused suspicion of being from another planet.
Grunting in satisfaction, he permitted himself the pleasure of being proud at having landed so near the cabin chosen as his goal. It had been a wise choice, this picking of so well isolated a place as a testing ground for the weapon. A wisp of smoke, a dark smudge against the rich blueness of the sky, attested to the cabin's occupancy. What he was about to do seemed fitting, for even the scientists of this planet had used animal life to test their own puny weapons. Now he, man, would be the guinea pig to prove the devastation to be wrought against all mankind native to this world.
He turned and spoke to someone within the lock. His language, while resembling no earthly tongue, was not much different than perhaps English to Chinese. It was foreign but not completely alien.
With the ease of a man accustomed to heavier gravity he went down the ladder easily, turning when he reached the ground to look up at the lock.