.

"We'll know soon," Reinhart said, half aloud.

Sherikov shot him a keen glance. "We'll know what? Let me in on it.
What's taking place?"

"We're in trouble. For twenty-four hours the machines haven't given
any reading at all. Nothing but a blank. A total blank."

Sherikov's features registered disbelief. "But that isn't possible.
_Some_ odds exist at all times."

"The odds exist, but the machines aren't able to calculate them."

"Why not?"

"Because a variable factor has been introduced. A factor which the
machines can't handle. They can't make any predictions from it."

"Can't they reject it?" Sherikov said slyly. "Can't they just--just
_ignore_ it?"

"No. It exists, as real data. Therefore it affects the balance of the
material, the sum total of all other available data. To reject it
would be to give a false reading. The machines can't reject any data
that's known to be true."

Sherikov pulled moodily at his black beard. "I would be interested in
knowing what sort of factor the machines can't handle. I thought they
could take in all data pertaining to contemporary reality."

"They can. This factor has nothing to do with contemporary reality.
That's the trouble. Histo-research in bringing its time bubble back
from the past got overzealous and cut the circuit too quickly. The
bubble came back loaded--with a man from the twentieth century. A man
from the past."

"I see. A man from two centuries ago." The big Pole frowned. "And with
a radically different Weltanschauung. No connection with our present
society. Not integrated along our lines at all. Therefore the SRB
machines are perplexed."

Reinhart grinned. "Perplexed? I suppose so. In any case, they can't do
anything with the data about this man. The variable man. No statistics
at all have been thrown up--no predictions have been made. And it
knocks everything else out of phase. We're dependent on the constant
showing of these odds. The whole war effort is geared around them."

"The horse-shoe nail. Remember the old poem? 'For want of a nail the
shoe was lost. For want of the shoe the horse was lost. For want of
the horse the rider was lost. For want--'"

"Exactly. A single factor coming along like this, one single
individual, can throw everything off. It doesn't seem possible that
one person could knock an entire society out of balance--but
apparently it is."

"What are you doing about this man?"

"The Security police are organized in a mass s