Admiral Garvie refilled the glass and passed it to me without a word, without a flicker of change in his expression. The old boy certainly knew how to play it cool.

"What you will find there," I went on, "are some of the most highly skilled men in the world in the fields of radar, radio, infrared, and electronic computers, operating the most advanced instruments ever used in those fields. We know now, never mind how, the count-down succession of signals the Russians use in the last minute before launching a missile. There's a huge dish aerial in Zebra that can pick up and amplify any such signals within seconds of its beginning. Then long-range radar and infrared home-in on that bearing and within three minutes of the rocket's lift-off they have its height, speed, and course pinpointed to an infinitesimal degree of error. The computers do this, of course. One minute later the information is in the hands of all the antimissile stations between Alaska and Greenland. One minute more and solidfuel infrared homing antimissile rockets are on their way: then the enemy missiles will be intercepted and harmlessly destroyed while still high over the Arctic regions. If you look at a map, you will see that in its present position Drift Ice Station Zebra is sitting practically on Russia's missile doorstep. It's hundreds of miles in advance of the present DEW line — the 'distant early warning' system. Anyway, it renders the DEW line obsolete."

"I'm only the office boy around those parts," Garvie said quietly. "I've never heard of any of this before."

I wasn't surprised. I'd never heard any of it myself, either, not until I'd just thought it up a moment ago. Commander Swanson's reactions, if and when we ever got to Drift Station Zebra, were going to be very interesting. But I'd cross that bridge when I came to it. At present, my only concern was to get there.