econd case, your subconscious
future memories are an added causal factor."

"And when I back-slip, after I've been needled, I generate a new
time-line? Is that it?"

Verkan Vall made a small sound of impatience. "No such thing!" he
exclaimed. "It's semantically inadmissible to talk about the total
presence of time with one breath and about generating new time-lines
with the next. _All_ time-lines are totally present, in perpetual
co-existence. The theory is that the EPC passes from one moment, on one
time-line, to the next moment on the next line, so that the true passage
of the EPC from moment to moment is a two-dimensional diagonal. So, in
the case we're using, the event of your going into the Martian Palace
exists on one time-line, and the event of your passing along to the
Starway exists on another, but both are events in real existence.

"Now, what we do, in paratime transposition, is to build up a
hypertemporal field to include the time-line we want to reach, and then
shift over to it. Same point in the plenum; same point in primary
time--plus primary time elapsed during mechanical and electronic lag
in the relays--but a different line of secondary time."

"Then why don't we have past-future time travel on our own time-line?"
the pilot wanted to know.

That was a question every paratimer has to answer, every time he talks
paratime to the laity. Verkan Vall had been expecting it; he answered
patiently.

"The Ghaldron-Hesthor field-generator is like every other mechanism; it
can operate only in the area of primary time in which it exists. It can
transpose to any other time-line, and carry with it anything inside its
field, but it can't go outside its own temporal area of existence, any
more than a bullet from that rifle can hit the target a week before it's
fired," Verkan Vall pointed out. "Anything inside the field is supposed
to be unaffected by anything outside. _Supposed to be_ is the way to put
it; it doesn't always work. Once in a while, something pretty nasty gets
picked up in transit." He thought, briefly, of the man in the black
tunic. "That's why we have armed guards at terminals."

"Suppose you pick up a blast from a nucleonic bomb," the pilot asked,
"or something red-hot, or radioactive?"

"We have a monument, at Paratime Police Headquarters, in Dhergabar,
bearing the names of our own personnel who didn't make it back. It's a
large monument; over the past ten thousand years, it's been inscribed