e any explanations long before that time."

"I see," Turnbull said flatly. "Mind operation. Is that what you did to
Scholar Duckworth?"

The expression on Scholar Rawling's face was so utterly different from
what Turnbull had expected that he found himself suddenly correcting
his thinking in a kaleidoscopic readjustment of his mind.

"What did you think you were on to, Dr. Turnbull?" the old man asked
slowly.

Turnbull started to answer, but, at that moment the door opened.

The round, pleasant-faced gentleman who came in needed no introduction
to Turnbull.

Scholar Duckworth said: "Hello, Dave. Sorry I wasn't here when you woke
up, but I got--" He stopped. "What's the matter?"

"I'm just cursing myself for being a fool," Turnbull said sheepishly. "I
was using your disappearance as a datum in a problem that didn't require
it."

Scholar Rawlings laughed abruptly. "Then you thought--"

Duckworth chuckled and raised a hand to interrupt Rawlings. "Just a
moment, Jason; let him logic it out to us."

"First take these straps off," said Turnbull. "I'm stiff enough as it
is, after being out cold for three days."

Rawlings touched a button on the wall, and the restraining straps
vanished. Turnbull sat up creakily, rubbing his arms.

"Well?" said Duckworth.

Turnbull looked up at the older man. "It was those first two letters of
yours that started me off."

"I was afraid of that," Duckworth said wryly. "I ... ah ... tried to get
them back before I left Earth, but, failing that, I sent you a letter to
try to throw you off the track."

"Did you think it would?" Turnbull asked.

"I wasn't sure," Duckworth admitted. "I decided that if you had what it
takes to see through it, you'd deserve to know the truth."

"I think I know it already."

"I dare say you do," Duckworth admitted. "But tell us first why you
jumped to the wrong conclusion."

Turnbull nodded. "As I said, your letters got me worrying. I knew you
must be on to something or you wouldn't have been so positive. So I
started checking on all the data about the City--especially that which
had come in just previous to the time you sent the letters.

"I found that several new artifacts had been discovered in Sector Nine
of the City--in the part they call the Bank Buildings. That struck a
chord in my memory, so I looked back over the previous records. That
Sector was supposed to have been cleaned out nearly ninety years ago.

"The error I made was in thin