of them, Quent Miles was walking quickly, reading all the street signs.
Suddenly he turned down a side street, and the two cadets raced after
him.

They were in the outskirts of the city now. Great areas were covered
with rolling grass fields where the citizens of Titan spent their
leisure hours playing ball and picnicking, and it was easy for the
cadets to follow the black-suited spaceman. They had to put on their
oxygen masks as the deadly fumes of the methane ammonia atmosphere began
to swirl around them. They were near the outer limits of the atmosphere
screen's effectiveness.

"I think he's going into that building up ahead, Astro," said Tom, his
voice distorted to a low metallic hiss by the miniature amplifier in the
face of the mask.

Astro nodded and they ducked into a gully as Quent Miles turned once
again and glanced down the street.

"Wonder what's in that building?" mused Tom.

"One way to find out," said Astro. "Come on. He's moving again."

The gas began to thicken now, and the two cadets found it difficult to
see more than a few feet ahead as they moved cautiously through the
swirling death around them. After what seemed like an hour, but was
actually hardly more than a few minutes, they found the building Miles
had entered.

"I'd give two weeks' leave for a ray gun now," said Tom.