ost human intricacy. Almost all the work of
the world, particularly in America, and most particularly in the
mechanical center of New York City, was done by machinery. And the
machinery itself was guided, handled, operated--even, in some
instances, constructed--by other, more intricate machines. They were
fashioned in pseudo-human form--thinking, logically acting,
independently acting mechanisms: the Robots. All but human, they
were--a new race. Inferior to humans, yet similar.

And in 2930 the machines, slaves of idle human masters, had been
developed too highly! They were upon the verge of a revolt!

All this Tina briefly sketched now to Larry. And to Larry it seemed a
very distant, very academic danger. Yet so soon all of us were plunged
into the midst of it!

The revolt had not yet come, but it was feared. A great Robot named
Migul seemed fomenting it. The revolt was smouldering; at any moment
it would burst; and then the machines would rise to destroy the
humans.

This was the situation when Harl and Tugh completed the Time-traveling
vehicles in this world. They had been tested, but never used. Then
Tugh had vanished; was gone now; and the larger of the two vehicles
was also gone.

Both Harl and Tina had always distrusted Tugh. They thought him allied
to the Robots. But they had no proof; and suavely he denied it, and
helped always with the Government activities struggling to keep the
mechanical slaves docile and at work.

* * * * *

Tugh and the larger vehicle had vanished, and so had Migul, the
insubordinate, giant mechanism--at which, unknown to the Government
officials, Tina and Harl had taken the other cage and started in
pursuit. It was possible that Tugh was loyal; that Migul had abducted
him and stolen the cage.

"Wait!" exclaimed Larry. "I'm trying to figure this out. It seems to
hang together. It almost does, but not quite. When did Tugh vanish
from your world?"

"To our consciousness," Tina answered, "about three hours ago. Perhaps
a little longer than that."

"But look here," Larry protested: "according to my story and that of
Mary Atwood, Tugh lived in 1935 and in 1777 for three years."

Confusing? But in a moment Larry understood it. Tugh could have taken
the cage, gone to 1777 and to 1935, alternated between them for what
was to him, and to those Time-worlds, three years--then have returned
to 2930 _on the same day of his departure_. He would have lived t