"Sir, there's been a nuclear explosion. We're checking the exact location now, but it appears to have been in the Denver area."

"Are you sure?" the President asked, fighting to keep calm.

"We're re-checking our instruments now, sir, but, yes, we're pretty sure. Sir, we don't know what happened or how it got there, but there was a nuclear explosion. I urge you to get to a place of safety at once while we try and figure out what's going on."

Fowler looked up. Neither TV picture had changed and now alarm klaxons were erupting all over the Presidential compound.

Offutt Air Force Base, just outside Omaha, Nebraska, was once known as Fort Crook. The former cavalry post had a splendid if somewhat anachronistic collection of red brick dwellings for its most senior officers, in the rear of which was stabling for the horses they no longer needed, and in front of which was a flat parade ground of sufficient size to exercise a regiment of cavalry. About a mile from that was the headquarters of the Strategic Air Command, a much more modern building with its own antique, a B-17 Flying Fortress of World War II, sitting outside. Also outside the building but below ground was the new command post, completed in 1989. A capacious room, local wags joked that it had been built because Hollywood's rendition of such rooms was better than the one SAC had originally built for itself, and the Air Force had decided to alter its reality to fit a fictional image.

Major General Chuck Timmons, Deputy Chief of Staff (Operations), had availed himself of the opportunity to stand his watch here instead of in his upstairs office, and had in fact been watching the Superbowl out of one eye on one of the eight large-screen TVs, but on two of the others had been real-time imagery from the Defense Support Program Satellites, called the DSPS birds, and he had caught the double-flash at Denver just as fast as everyone else. Timmons dropped the pencil he'd been working with. Behind his battle-staff seat were several glassed-in rooms - there were two levels of such rooms - which contained the fifty or so support personnel who kept SAC operating around the clock. Timmons lifted his phone and punched the button for the senior intelligence officer.

"I see it, sir."

"Possible mistake?"

"Negative, sir, test circuitry says the bird's working just fine."

"Keep me posted." Timmons turned to his deputy. "Get the boss in here. Beep everybody, I want a full emergency-action team and a full battle-staff - and I want it now!" To his operations officer: "Get Looking Glass up now! I want the alert wings postured for takeoff, and I want an immediate alert flashed to everybody."

In the glassed-in room behind the General and to his left, a sergeant pushed a few buttons. Though SAC had long since ceased keeping aircraft in the air around the clock, thirty percent of SAC's aircraft were typically kept on alert status at any time. The order out to the alert wings was sent by land-line and used a computer-generated voice, because it had been decided that a human might get excited and slur his words. The orders took perhaps twenty seconds to be transmitted, and the operations officers at the alert wings were galvanized to action.