Brigands of the Moon by Raymond King Cummings description:
Gregg Haljan was aware that there was a certain danger in having the giant spaceship Planetara stop off at the moon to pick up Grantline's special cargo of moon ore. For that rare metal–invaluable in keeping Earth's technology running–was the target of many greedy eyes. But nevertheless he hadn't figured on the special twist the clever Martian brigands would use. So when he found both the ship and himself suddenly in their hands, he knew that there was only one way in which he could hope to save that cargo and his own secret–that would be by turning space-pirate himself and paying the Brigands of the Moon back in their own interplanetary coin.
istle nearby sounded. The figure was making off! My pencil ray was in my hand and I pressed its switch. The tiny heat ray stabbed through the air, but I missed. The figure stumbled but did not fall. I saw a bare gray arm come from the cloak, flung up to maintain its balance. Or perhaps my pencil ray had seared his arm. The gray-skinned arm of a Martian.
Snap was shouting, "Give him another!" But the figure passed beyond the actinic glare and vanished.
We were detained in the turmoil of the corridor for ten minutes or more with official explanations. Then a message from Halsey released us. The Martian who had been following us in his invisible cloak was never caught.
We escaped from the crowd at last and made our way back to the Planetara, where the passengers were already assembling for the outward Martian voyage.
I stood on the turret balcony of the Planetara with Captain Carter and Dr. Frank, the ship surgeon, watching the arriving passengers. It