The Stranger by Gordon R. Dickson - If the alien space craft was not a rocket ship, what was it? And an even bigger question: should they investigate-or run for their lives!

We will not consider the odds involved in their finding the stranger, for the odds were impossible.

They came down to rest their tubes on an unnamed planet of a little-known star in the Buckhorn Cluster. Because they were tired from weeks in space, they came in without looking. They circled the planet once and spiraled down to an open patch of sand between two rocky cliffs. Only then did they see the other ship.

Jeff Wadley was at the controls and his eyes widened when he saw it. But his fingers did not hesitate on the controls, for a deep-space starship is not the kind of vehicle that can change its mind about landing once it is within half a mile of the ground. He brought the Emerald Girl in smoothly to a stop not five hundred feet from the stranger. Then he sat back.

"Dad," he said flatly, into the intercom, "swing the turret!"

Peter Wadley, up in the instrument room, had already seen the strange ship, and the heavy twin barrels of the automatic rifles were depressing to cover. Jeff leaned forward to the communicator.

"Identify yourself!" The tight beam in Common Code snapped across the little stretch of open sand to the cliff against which the other seemed to nestle. "We are the mining ship Emerald Girl, Earth license, five hundred and eighty-two days out of Arcturus Station. Identify yourself!"

There were steps behind Jeff, and Peter Wadley came to stand behind his son's tense back.

"Do they answer, Jeff?"

"No."

"Identify yourself. Identify yourself! Identify yourself!"

The angry demand crackled and arced invisibly across the space between both vessels. And there was no answer.