leave me that battery."

"You won't get away with it," she told him again, calmly this time.

"No," he admitted. "Probably not. But maybe the human race will, if I
have time to find an answer to the plague you won't see under your nose.
But you won't get away with it, either. In the long run, your kind never
do."

Molly was sniffling as they drove away. It had probably been the best
life she'd known, Doc supposed. Chris could be kind to menials. But now
Molly's work was done, and she'd have to disappear into the villages. He
let her off at the first village and drove on alone. He was itching to
get to the microscope now, hardly able to wait through the long journey
back to Jake. His impatience grew with each mile.

Finally he gave up. He swung the tractor into a small gulley between
sand dunes, left the motor idling and pulled down the shades the
villagers used for blackout traveling. There was power enough for the
mike here, and the cab was big enough for what he had to do.

He mounted the mike on the tractor seat and began laying out the
collection of smears and cultures he had brought. It had been years
since he'd made a film for the electron mike, but he found it all came
back to him as he worked.

His hands were sweating with tension as he inserted the first film into
the chamber. He had the magnetic "lenses" set for twenty thousand power,
but a quick glance showed it was too weak. He raised the power to fifty
thousand.

The filaments were there, clear and distinct.

He turned on the little tape recorder that had been part of Chris'
equipment and set the microphone where he could dictate into it without
stopping to make clumsy notes. He readjusted the focus carefully,
carrying on a running commentary.

Then he gasped. Each of the little filaments carried three tiny darker
sections; each was a cell, complete in itself, with the typical Martian
triple nucleus.

He put a film with a tiny section of the nerve tissue from a corpse into
the chamber next, and again a quick glance at the screen was enough. The
filaments were there, thickly crowded among nerve cells. They _did_
travel along the nerves to reach the base of the brain before the larger
lump could form.

A specimen from one of the black specks was even more interesting. The
filaments were there, but some were changed or changing into tiny, round
cells, also with the triple dark spots of nuclei. Those must be the
final form that was released to inf