ciousness he wondered impersonally about the dying
pain in his head and how he came to be where he was. He could remember
only about a strange thing in the sky, and a great fear.

Then it burst upon him in full recollection--the comet, the dust, the
laboratory. They had proved the dust that was in the comet's tail had
accumulated in the metal surfaces of the failed engines. What more did
they need to prove the comet's responsibility?

He slept, and when he awoke his father was there. "Hi, Son," Professor
Maddox said.

Ken smiled weakly. "Hi, Dad."

Dr. Adams wouldn't let them talk much, and he didn't want Ken's father
to tell him why he was there. He wanted Ken to dredge out of his own
memories the circumstances of the attack.

Ken said, "I've got to get out of here. Things must be getting behind at
the lab. Have you found anything new?"

"Take it easy," his father said. "We've got a little better picture of
what we're up against. The dust is quite definitely from the comet's
tail. It has a very large molecule, and is suspended in our atmosphere
in colloidal form. Its basis is a transuranic element, which is,
however, only slightly radioactive. By volume, it is present in the
amount of about one part in ten million, which is fairly heavy
concentration for an alien substance of that kind.

"Perhaps the most important thing we've found is that it has a strong
affinity for metals, so that its accumulation on metallic surfaces is
much higher than in the general atmosphere."

"It would!" Ken said, with a vague attempt at humor. "Why couldn't it
have had an affinity for old rubber tires, or secondhand galoshes?

"How late is it? Can I get up to the lab this afternoon?" Ken struggled
to a sitting position. A gigantic pain shot through his head and down
his spinal column. He felt as if his head were encased in a cement
block. He fell back with a groan.

"Don't try that again for a few days!" his father said severely. "You're
not going anywhere for quite a while. I have to go now, but your mother
will be in tonight. Maria will come, too. You do what the doctors and
nurses tell you to!"

"Dad--why am I here?" He moaned in agony of both spirit and body.

"You had an accident," said Dr. Adams smoothly. "It will all come back
to you and you'll soon be fine."

Ken watched his father disappear through the doorway. He felt the sting
of a needle in his arm and was aware the nurse was standing near. He
wanted to talk some