ng structure of alloy--jammed on his
brakes--stopped beside a soldier who, as soon as Kinnison jumped off,
mounted the motorcycle and drove it away.

Kinnison dashed up to an apparently blank wall, turned his back upon
four commissioned officers holding cocked forty-fives at the ready, and
fitted his right eye into a cup. Unlike fingerprints, retinal patterns
cannot be imitated, duplicated, or altered; any imposter would have died
instantly, without arrest or question. For every man who belonged
aboard that rocket had been checked and tested--_how_ he had been
checked and tested!--since one spy, in any one of those Technos' chairs,
could wreak damage untellable.

The port snapped open. Kinnison climbed a ladder into the large, but
crowded, Operations Room.

"Hi, Teddy!" a yell arose.

"Hi, Walt! Hi-ya, Red! What-ho, Baldy!" and so on. These men were
friends of old.

"Where are they?" he demanded. "Is our stuff getting away? Lemme take a
peek at the Ball!"

"I'll say it is! O.K., Ted, squeeze in here!"

He squeezed in. It was not a ball, but a hemisphere, slightly oblate and
centered approximately by the North Pole. A multitude of red dots moved
slowly--a hundred miles upon that map was a small distance--northward
over Canada; a closer-packed, less numerous group of yellowish-greens,
already on the American side of the Pole, was coming south.

As had been expected, the Americans had more missiles than did the
enemy. The other belief, that America had more adequate defenses and
better-trained, more highly skilled defenders, would soon be put to
test.

A string of blue lights blazed across the continent, from Nome through
Skagway and Wallaston and Churchill and Kaniapiskau to Belle Isle;
America's First Line of Defense. Regulars all. Ambers almost blanketed
those blues; their combat rockets were already grabbing altitude. The
Second Line, from Portland, Seattle, and Vancouver across to Halifax,
also showed solid green, with some flashes of amber. Part Regulars; part
National Guard.

Chicago was in the Third Line, all National Guard, extending from San
Francisco to New York. Green--alert and operating. So were the Fourth,
the Fifth, and the Sixth. Operation Bullfinch was clicking; on schedule
to the second.

A bell clanged; the men sprang to their stations and strapped down.
Every chair was occupied. Combat Rocket Number One Oh Six Eight Five,
full-powered by the disintegrating nuclei of unstable isotopes, to