"It shows one thing," Ketrik said, studying the film. "Dar Vaajo's had a wall built completely around the city. That wasn't there eight years ago! And those towers stationed around the wall—what do you suppose they are?"
"Control towers. That's an electronic wall! And you'll observe there's another within the city itself, surrounding that group of buildings which must be the laboratories. Ketrik—if you ever get in there...." His voice dwindled away in doubt.
"You don't think I can do it? I don't either, Mark—not as an Earthman!"
"Come. We'll fix that."
They passed through endless corridors, arrived finally at a large white-enameled room. It was complete with operating tables, instruments, plastics, ray-lamps—everything necessary to Earth's espionage system.
Ketrik stripped piecemeal, allowed every inch of his superbly muscled body to be subjected to the stinging Ulmo lamps. Gradually under the hot rays, the very pigmentation of his skin changed to the deep reddish-copper of a Martian. Mark proved himself an expert at this. Even the insides of Ketrik's ears did not escape the ray.
"Don't worry," Mark told him. "This will all wear off eventually."
"Yes? How long?"
"In about two years! Now, your eyes. You never saw a Martian with gray eyes. Look up just a moment."
A few drops of liquid, a harmless vegetable composition, changed Ketrik's eyes to a muddy golden color.