h up. He had been speaking less than five
minutes when a student by the name of Marvin Green jumped to his feet in
great excitement, waving his hand and shouting, "Dr. Grant! Dr. Grant!"

Dr. Grant had stopped his lecture and frowned darkly, then said, "If you
will please take your seat--"

"But Dr. Grant!" Marvin Green had interrupted him excitedly. "I've got
it! I've got it!"

What had happened then was impossible for the mind to accept. Marvin
Green had simply ceased to be.

There had been a stunned silence. And in that silence, it went on.
Student after student popping out of existence in what seemed to be a
chain reaction.

He wasn't aware when Dr. Grant vanished. All he knew was that when at
last he was alone he looked toward the podium and the professor was also
gone.

He kept waiting to go himself. When he didn't, he lost the fear that had
rooted him to the spot, and rushed to the exit where he at first tried
to break down the door and make his escape, then subsided into pounding
and shouting for help when he realized his physical strength was
insufficient for the job.

Questioning didn't bring out any additional fact, nor alter any
statement. There had been no sound to the vanishing, no movement of the
person that could be considered significant, no flashes of light, no
strange odors. Nothing.

* * * * *

Fred Grant got the flash on his hot rod radio on the way home from high
school.

At the end of the report Fred wrote down Mark Smythe's address on a
scrap of paper, and drove home to be with his mother. It was three days
before he could get away.

On the morning of the third day, his aunt Emily arrived to take charge
of things, and he was able to slip away. He drove immediately to Mark
Smythe's address. It was one of the better class rooming houses near the
campus. The land-lady wasn't going to let him in nor announce him until
he explained he was the son of the professor who had vanished. She
immediately swung to the other extreme and didn't bother to find out if
Mark wanted to see him.

"My father was your teacher," Fred said.

"Oh? Come on in."

There were tennis rackets. On the bookshelves there were tennis books.
On a table there was a tennis trophy. Otherwise there was just a bed, a
rug, and two or three chairs.

"I don't know what I can tell you more than I've already told the police
and the reporters," Mark said apologetically. "I guess it's tough,
l