e of only one thing--the
tunnel went somewhere. Martians or Russians, fantastic plot or crazy
hallucination, whatever was wrong with Tylerton had an explanation,
and the place to look for it was at the end of the tunnel.

They jogged along. It was more than a mile before they began to see an
end. They were in luck--at least no one came through the tunnel to
spot them. But Swanson had said that it was only at certain hours that
the tunnel seemed to be in use.

Always the fifteenth of June. Why? Burckhardt asked himself. Never
mind the how. _Why?_

And falling asleep, completely involuntarily--everyone at the same
time, it seemed. And not remembering, never remembering
anything--Swanson had said how eagerly he saw Burckhardt again, the
morning after Burckhardt had incautiously waited five minutes too many
before retreating into the darkroom. When Swanson had come to,
Burckhardt was gone. Swanson had seen him in the street that
afternoon, but Burckhardt had remembered nothing.

And Swanson had lived his mouse's existence for weeks, hiding in the
woodwork at night, stealing out by day to search for Burckhardt in
pitiful hope, scurrying around the fringe of life, trying to keep from
the deadly eyes of _them_.

Them. One of "them" was the girl named April Horn. It was by seeing
her walk carelessly into a telephone booth and never come out that
Swanson had found the tunnel. Another was the man at the cigar stand
in Burckhardt's office building. There were more, at least a dozen
that Swanson knew of or suspected.

They were easy enough to spot, once you knew where to look--for they,
alone in Tylerton, changed their roles from day to day. Burckhardt was
on that 8:51 bus, every morning of every day-that-was-June-15th, never
different by a hair or a moment. But April Horn was sometimes gaudy in
the cellophane skirt, giving away candy or cigarettes; sometimes
plainly dressed; sometimes not seen by Swanson at all.

Russians? Martians? Whatever they were, what could they be hoping to
gain from this mad masquerade?

Burckhardt didn't know the answer--but perhaps it lay beyond the door
at the end of the tunnel. They listened carefully and heard distant
sounds that could not quite be made out, but nothing that seemed
dangerous. They slipped through.

And, through a wide chamber and up a flight of steps, they found they
were in what Burckhardt recognized as the Contro Chemicals plant.

* * * *