ve gone wild. They're--_"

Calhoun seated himself at the control desk. He threw switches there.
He momentarily touched a button. There was a slight shock and the
beginning of a roar outside. It cut off. Calhoun looked at the vision
plates showing outside. There was swirling smoke and steam. There were
men running in headlong flight, leaving their ground cars behind them.

"A slight touch of emergency rocket," said Calhoun. "They've run away.
Now we end the plague on Tallien Three."

The grid operator was still dazed by the continued absence of any
indication that he might ever become a para. He said unsteadily:

"Sure! Sure! But how?"

"Wood smoke," said Calhoun. "Emergency rockets. Roofs! There's been no
wood smoke in the air on this planet because there are no forest fires
and people don't burn fuel. They use electricity. So we start the
largest production of wood smoke that we find convenient, and the
population of a certain modified butyl mercaptan molecule will be
reduced. Down to a normal level. Immediately!"

The emergency rocket bellowed thunderously and the little Med Ship
rose.

* * * * *

There have been, of course, emergency measures against contagion all
through human history. There was a king of France, on Earth, who had
all the lepers in his kingdom killed. There have been ships and houses
burned to drive out plague, and quarantines which simply interfered
with human beings were countless. Calhoun's measure on Tallien was
somewhat more dramatic than most, but it had good justification.

He set fire to the planet's capital city. The little Med Ship swept
over the darkened buildings. Her emergency rockets made thin pencils
of flame two hundred feet long. She touched off roofs to the east, and
Calhoun rose to see which way the wind blew. He descended and touched
here and there....

Thick, seemingly suffocating masses of wood smoke flowed over the
city. They were not actually strangling, but they created panic. There
was fighting in Government Center, but it stopped when the mysterious
stuff--not one man in a hundred had ever seen burning wood or smelled
its smoke--the fighting stopped and all men fled when a choking,
reeking blanket rolled over the city and lay there.

It wasn't a great fire, considering everything. Less than ten per cent
of the city burned, but ninety-odd per cent of the paras in it ceased
to be paras. More, they had suddenly regained an invincibl