the corridor with MacHeath.
"That man is scared silly! But what an actor! You'd never know he was
eating his guts out."

"Sure he's scared," MacHeath said. "With all this sabotage talk going
around, he's afraid there'll be an exhaustive investigation, and he
can't take that right now."

Griffin frowned. "I guess I missed that. What did you pick up?"

"He's supposed to meet a Soviet agent tonight, and he's afraid he'll
be caught. He doesn't know what happened to the first three, and he
won't know what will happen to Number Four tonight.

"We'll keep him around as long as he's useful. He's not a Bohr or a
Pauli or a Fermi, but he--"

MacHeath stopped himself suddenly and came to a dead halt.

"My God," he said softly, "that's _it_."

His hunch had hatched.

After a moment, he said: "Harry is getting back from the target end of
the tube now, Bill. He can't pick me up, so beetle it down to the tool
room, get him, and get up to the workshop fast. If I'm not there,
wait; I have a little prying to do."

[Illustration]

"Can do," said Griffin. He went toward the elevator at an easy lope.

David MacHeath went in the opposite direction.

* * * * *

When MacHeath returned to the workshop which he had been assigned,
Bill Griffin and Harry Benbow were waiting for him. Beside the
big-muscled Griffin, Harry Benbow looked even thinner than he was. He
was a good six-two, which made him a head taller than Griffin, but,
unlike many tall, lean men, Benbow had no tendency to slouch; he stood
tall and straight, reminding MacHeath of a poplar tree towering
proudly over the countryside. Benbow was one of those rare American
Negroes whose skin was actually as close to being "black" as human
pigmentation will allow. His eyes were like disks of obsidian set in
spheres of white porcelain, which gave an odd contrast-similarity
effect when compared with Griffin's china-blue eyes.

If the average man had wanted to pick two human beings who were
"opposites," he could hardly have made a better choice than Benbow and
the short, thickly-built, blond-haired, pink-skinned Bill Griffin. But
the average man would be so struck by the differences that he would
never notice that the similarities were vastly more important.

"You look as if you'd just been kissed by Miss America," Harry said as
MacHeath came through the door.

"Better than that," MacHeath said. "We've got work to do."

"What's the pitch?" Grif