is mental and not physical?"

"Exactly," Dodd said.

Inside the house they found one room outfitted as a home office. "I
have an office downtown," the doctor explained, "but I also use this
one a few afternoons a week. Now, who can tell me about this?" His
eyes were on Marks, and as he talked, he reached for the scientist's
wrist.

Tom Dodd explained carefully, "He was suddenly stricken. We were with
him. We don't know what happened, except that he made sense one
minute, but talked only garbled words the next."

Chavez took an otoscope, an instrument used to examine eyes, ears,
nose, and throat, and switched on the tiny light. He flicked it into
Marks' eyes and watched the behavior of the pupils. Then he listened
with a stethoscope. A little rubber hammer came out next and was
applied to the reflexes of the stricken scientist. The reflexes looked
normal to Rick.

Dr. Marks suddenly looked up and began spouting gibberish. Rick
winced.

Chavez listened gravely, apparently not at all disturbed. The flow of
meaningless words ceased and Rick sighed with relief. He saw that
Scotty had been equally affected.

"What is your specialty, Doctor?" Dodd asked.

"I'm a neurologist."

That was good, Rick thought. A neurologist was exactly what Marks
seemed to need.

"Do you make anything of this?" Dodd asked.

The doctor shook his head. "Nothing. I've never seen a case like it.
I've never even heard of one. In fact, I know of only one analogue,
and it's an electronic one. Do you know how computers work? The big
electronic brains?"

The three nodded.

"Then you will understand. I have worked with computers, and now and
then one of them suddenly starts turning out gibberish for no apparent
reason. A check of the circuits may show that everything is
functionally normal. Yet, the gibberish continues. Often it clears up,
with no more reason than it started. Sometimes this happens when the
machine is cold, before it is properly warmed up. At other times, it
happens when the machine is tired."

"Tired?" Dodd looked his disbelief. "Machines don't get tired. Not in
those terms."

Chavez smiled. "Perhaps not. Yet, to those who work with them, it does
sometimes appear that the machine is tired. There is really no other
expression for it."

Rick knew something of this through his association with Dr. Parnell
Winston of the Spindrift staff. Winston was an expert in the new
science of cybernetics, which is defined as the sc