, extended it slowly into a hypothesis.
After three more years, a lucky accident put the final proofs into his
hands.

He had invented a most effective longevity drug. It was not proof
against violence; aside from that, however, it could fairly be called an
immortality serum.

* * * * *

Now was the time for caution. But years of seclusion had made Dennison
unwary of people and their motives. He was more or less heedless of the
world around him; it never occurred to him that the world was not
equally heedless of him.

He thought only about his serum. It was valuable and patentable. But was
it the sort of thing that should be revealed? Was the world ready for an
immortality drug?

He had never enjoyed speculation of this sort. But since the atom bomb,
many scientists had been forced to look at the ethics of their
profession. Dennison looked at his and decided that immortality was
inevitable.

Mankind had, throughout its existence, poked and probed into the
recesses of nature, trying to figure out how things worked. If one man
didn't discover fire, or the use of the lever, or gunpowder, or the atom
bomb, or immortality, another would. Man willed to know all nature's
secrets, and there was no way of keeping them hidden.

Armed with this bleak but comforting philosophy, Dennison packed his
formulas and proofs into a briefcase, slipped a two-ounce bottle of the
product into a jacket pocket, and left his Riverdale laboratory. It was
already evening. He planned to spend the night in a good midtown hotel,
see a movie, and proceed to the Patent Office in Washington the
following day.

On the subway, Dennison was absorbed in a newspaper. He was barely
conscious of the men sitting on either side of him. He became aware of
them only when the man on his right poked him firmly in the ribs.

Dennison glanced over and saw the snub nose of a small automatic,
concealed from the rest of the car by a newspaper, resting against his
side.

"What is this?" Dennison asked.

"Hand it over," the man said.

Dennison was stunned. How could anyone have known about his discovery?
And how could they dare try to rob him in a public subway car?

Then he realized that they were probably just after his money.

"I don't have much on me," Dennison said hoarsely, reaching for his
wallet.

The man on his left leaned over and slapped the briefcase. "Not money,"
he said. "The immortality stuff."

*