The Aliens — Murray Leinster

The human race was expanding through the galaxy … and so, they knew, were the Aliens. When two expanding empires meet … war is inevitable. Or is it …? At 04 hours 10 minutes, ship time, the Niccola was well inside the Theta Gisol solar system. She had previously secured excellent evidence that this was not the home of the Plumie civilization. There was no tuned radiation. There was no evidence of interplanetary travel -- rockets would be more than obvious, and a magnetronic drive had a highly characteristic radiation-pattern -- so the real purpose of the Niccola's voyage would not be accomplished here. She wouldn't find out where Plumies came from.