the brittle stalks of skit-trees, and then of upward acceleration so fierce that it was like a blow. The atmosphere-flier hurtled skyward with all its lift-jets firing full blast, and there was the Galloping Cow lumbering ungracefully through atmosphere at ten thousand feet, some twelve or more miles away.

McRae's voice came out of a communicator which now picked up no static whatever.

"What the devil?" he boomed. "We saw something that looked like a big metal tank, and it vanished and you went skyward from where it'd been like a bat out of a cave."

"Suppose you follow me," said Wentworth grimly. "The skit-tree planters on this planet, anyhow, don't want us around. By pure accident, I got a line on where they were. They lured me away from their place by projecting a city.

"I went to look, and it vanished. I played hide and seek with it until they changed tactics and let it stay in existence. Maybe they thought we'd land on it, high up, and get out of the flier to explore.

"Then the city would have vanished and we'd have dropped a mile or two, hard. But we landed on the ground instead, and they clapped a jail around us.

"I don't know what they intended, but you came along and they let the jail vanish to keep you from examining it. And now we'll go talk to them!"

The flier was streaking vengefully back to the embankment to where only that morning, before sunrise, Wentworth had seen something he still didn't like to think about.

The Galloping Cow veered around to follow, with all the elephantine grace of the animal for which she had been unofficially christened. She'd been an Earth-Pluto freighter before conversion for the expedition, and she was a staunch vessel, but not a handy one.

The flier dived for the hills. Wentworth's jaws were hard and angry. The Galloping Cow trailed, wallowing. The flier quartered back and forth across the hills, examining every square inch of ground.

Nothing. Absolutely nothing. The search went on. The communicator boomed.

"They're playing 'possum," McRae's voice said. "We'll land and make a camp and prepare to hunt on foot."

Wentworth growled angrily. He continued to search. Deeper and deeper the flier went into the hills, going over and over every bit of terrain. Then, quite suddenly, the 

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