hematics."

"Oh, arithmetic."

"No," Stutsman said. "Mathematics. You see? You don't even know the
difference between the two, so what good would the papers do you?"

Scorio nodded. "Yeah, you're right."

_CHAPTER ELEVEN_

The Paris-Berlin express thundered through the night, a gigantic ship
that rode high above the Earth. Far below one could see the dim lights
of eastern Europe.

Harry Wilson pressed his face against the window, staring down. There
was nothing to see but the tiny lights. They were alone, he and the
other occupants of the ship ... alone in the dark world that surrounded
them.

But Wilson sensed some other presence in the ship, someone besides the
pilot and his mechanics up ahead, the hostess and the three stodgy
traveling men who were his fellow passengers.

Wilson's hair ruffled at the base of his skull, tingling with an unknown
fear that left him shaken.

A voice whispered in his ear: "Harry Wilson. So you are running away!"

Just a tiny voice that seemed hardly a voice at all, it seemed at once
to come from far away and yet from very near. The voice, with an edge of
coldness on it, was one he never would forget.

He cowered in his seat, whimpering.

The voice came again: "Didn't I tell you that you couldn't run away?
That no matter where you went, I'd find you?"

"Go away," Wilson whispered huskily. "Leave me alone. Haven't you
hounded me enough?"

"No," answered the voice, "not enough. Not yet. You sold us out. You
warned Chambers about our energy and now Chambers is sending men to kill
us. But they won't succeed, Wilson."

"You can't hurt me," said Wilson defiantly. "You can't do anything but
talk to me. You're trying to drive me mad, but you can't. I won't let
you. I'm not going to pay any more attention to you."

The whisper chuckled.

"You can't," argued Wilson wildly. "All you can do is talk to me. You've
never done anything but that. You drove me out of New York and out of
London and now you're driving me out of Paris. But Berlin is as far as I
will go. I won't listen to you any more."

"Wilson," whispered the voice, "look inside your bag. The bag, Wilson,
where you are carrying that money. That stack of credit certificates.
Almost eleven thousand dollars, what is left of the twenty thousand
Chambers paid you."

With a wild cry Wilson clawed at his bag, snapped it open, pawed through
it.

* * * * *

The credit certificates wer