All Cats Are Gray by Andre Norton (finding audrey txt) 📕

Her voice quavered and she raised her chin with a new air Cliff had never seen before—a sort of proud acceptance. She pushed back her wandering hair, but she made no move to imprison it under the heavy net again.

“That is why I saw the thing when it crossed between us. Against your spaceall it was another shade of gray—an outline. So I put out mine and waited for it to show against that—it was our only chance, Cliff.

“It was curious at first, I think, and it knew we couldn’t see it—which is why it waited to attack. But when Bat’s actions gave it away it moved. So I waited to see that flicker against the spaceall and then I let him have it. It’s really very simple….”

Cliff laughed a bit shakily. “But what was this gray thing? I don’t get it.”

“I think it was what made the Empress a derelict. Something out of space, maybe, or from another world somewhere.” She waved her hands. “It’s invisible because it’s a color beyond our range of sight. It must have stayed in here all these years. And it kills—it must—when its curiosity is satisfied.” Swiftly she described the scene in the cabin and the strange behavior of the gem pile which had betrayed the creature to her.

Cliff did not return his blaster to its holder. “Any more of them on board, d’you think?” He didn’t look pleased at the prospect.

Steena turned to Bat. He was paying particular attention to the space between two front toes in the process of a complete bath. “I don’t think so. But Bat will tell us if there are. He can see them clearly, I believe.”

But there weren’t any more and two weeks later Cliff, Steena and Bat brought the Empress into the Lunar quarantine station. And that is the end of Steena’s story because, as we have been told, happy marriages need no chronicles. And Steena had found someone who knew of her gray world and did not find it too hard to share with her—someone besides Bat. It turned out to be a real love match.

The last time I saw her she was wrapped in a flame-red cloak from the looms of Rigel and wore a fortune in Jovan rubies blazing on her wrists. Cliff was flipping a three-figure credit bill to a waiter. And Bat had a row of Vernal juice glasses set up before him. Just a little family party out on the town.