g it would take a man to
go nuts in isolation. On the voyage back, he was not aboard the
_Woonsocket_ at all, and no one missed him because only the captain and
two other Navy men had known he was aboard, and they knew that he had been
dropped overboard at Istanbul.

The sleek, tapered cylindroid might easily have been mistaken for a Naval
torpedo, since it was roughly the same size and shape. Actually, it was a
sort of hybrid, combining the torpedo and the two-man submarine that the
Japanese had used in World War II, plus refinements contributed by such
apparently diverse arts as skin-diving, cybernetics, and nucleonics.

Inside this one-man underwater vessel, Raphael Poe lay prone, guiding the
little atomic-powered submarine across the Black Sea, past Odessa, and up
the Dnieper. The first leg, the four hundred miles from the Bosporous to
the mouth of the river, was relatively easy. The two hundred and sixty
miles from there to the Dnepropetrovsk was a little more difficult, but
not terribly so. It became increasingly more difficult as the Dnieper
narrowed and became more shallow.

On to Kiev. His course changed at Dnepropetrovsk, from northeast to
northwest, for the next two hundred fifty miles. At Kiev, the river
changed course again, heading north. Three hundred and fifty miles farther
on, at Smolensk, he was heading almost due east.

It had not been an easy trip. At night, he had surfaced to get his
bearings and to recharge the air tanks. Several times, he had had to take
to the land, using the caterpillar treads on the little machine, because
of obstacles in the river.

At the end of the ninth day, he was still one hundred eighty miles from
Moscow, but, at that point, he got out of the submarine and prepared
himself for the trip overland. When he was ready, he pressed a special
button on the control panel of the expensive little craft. Immediately,
the special robot brain took over. It had recorded the trip upstream; by
applying that information in reverse--a "mirror image," so to speak--it
began guiding itself back toward Istanbul, applying the necessary
corrective factors that made the difference between an upstream and a
downstream trip. If it had made a mistake or had been discovered, it would
have blown itself to bits. As a tribute to modern robotics and
ultra-microminiaturization, it is a fact that the little craft was picked
up five days later a few miles from Istanbul by the U.S.S. _Paducah_.

By tha