y, Mason," he said.
"Sit down and explain yourself."

But Mason didn't sit down. He thrust his hand in his pocket, pulled out
the piece of black stone he had chipped off the image in the cavern and
handed it to Norris.

"Take a look at that!" he demanded.

Norris took the stone, glanced at it and laid it down on his desk. His
face was emotionless. "I expected this sooner or later," he said. "Yes,
it's _Indurate_ all right. Is that what you want me to say?"

There was a dangerous fanatical glint in Mason's eyes now. With a sudden
quick motion he pulled out his heat pistol.

"So you tricked us!" he snarled. "Why? I want to know why."

I stepped forward and seized Mason's gun hand. "Don't be a fool," I
said. "It can't be that important."

Mason threw back his head and burst into an hysterical peal of laughter.
"Important!" he cried. "Tell him how important it is, Norris. _Tell
him._"

Quietly the Navigator filled and lighted his pipe. "I'm afraid Mason is
right," he said. "I did trick you. Not purposely, however. And in the
beginning I had no intention of telling anything but the truth. Actually
we're here because of a dead man's vengeance."

Norris took his pipe from his lips and stared at it absently.

"You'll remember that Ganeth-Klae, the Martian, and I worked together to
invent _Indurate_. But whereas I was interested in the commercial
aspects of that product, Klae was absorbed only in the experimental
angle of it. He had some crazy idea that it should not be given to the
general public at once, but rather should be allocated for the first few
years to a select group of scientific organizations. You see, _Indurate_
was such a departure from all known materials that Ganeth-Klae feared it
would be utilized for military purposes.

"I took him for a dreamer and a fool. Actually he was neither. How was I
to know that his keen penetrating brain had seen through my motive to
get control of all commercial marketing of _Indurate_? I had laid my
plans carefully, and I had expected to reap a nice harvest. Klae must
have been aware of my innermost thoughts, but Martian-like he said
nothing."

Norris paused to wet his lips and lean against the desk. "I didn't kill
Ganeth-Klae," he continued, "though I suppose in a court of law I would
be judged responsible for his death. The manufacture of _Indurate_
required some ticklish work. As you know, we produced our halves of the
formula separately. Physical contact with my