Don't Look Now by Henry Kuttner - That man beside you may be a Martian. They own our world, but only a few wise and far-seeing men like Lyman know it!
The man in the brown suit was looking at himself in the mirror behind the bar. The reflection seemed to interest him even more deeply than the drink between his hands. He was paying only perfunctory attention to Lyman’s attempts at conversation. This had been going on for perhaps fifteen minutes before he finally lifted his glass and took a deep swallow.
“Don’t look now,” Lyman said.
The brown man slid his eyes sidewise toward Lyman; tilted his glass higher, and took another swig. Ice-cubes slipped down toward his mouth. He put the glass back on the red-brown wood and signaled for a refill. Finally he took a deep breath and looked at Lyman.
“Don’t look at what?” he asked.
“There was one sitting right beside you,” Lyman said, blinking rather glazed eyes. “He just went out. You mean you couldn’t see him?”
The brown man finished paying for his fresh drink before he answered. “See who?” he asked, with a fine mixture of boredom, distaste and reluctant interest. “Who went out?”
“What have I been telling you for the last ten minutes? Weren’t you listening?”
“Certainly I was listening. That is—certainly. You were talking about—bathtubs. Radios. Orson—”
“Not Orson. H. G. Herbert George. With Orson it was just a gag. H. G. knew—or suspected. I wonder if it was simply intuition with him? He couldn’t have had any proof—but he did stop writing science-fiction rather suddenly, didn’t he? I’ll bet he knew once, though.”
“Knew what?”
