A Quiet Night Aboard the ISS

There it was again, the scratching that should not be—an insistent itching sound like wind-blown branches playing over the frame of an attic window, searching for a way inside.

But there is no attic; only the wide, hexagonal cupola of the space station. And there was no breeze nor branches in the cold dark of space. And there is certainly nothing testing the cracks and seams of the station, searching for a way in.

Is there?
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I'd like to thank my friend Jimmie Bise (https://www.facebook.com/JimmieWrites/) for writing the story to go with my spooky Weekly Warm-up.