THERE WAS A BOMB on the Leystrasse, level forty-five, right outside the Bagatelle Flower and Gift Shoppe, about a hundred meters down the promenade from Prosperity Plaza.

"I am a bomb," the bomb said to passersby. "I will explode in four hours, five minutes, and seventeen seconds. I have a force equal to fifty thousand English tons of trinitrololuene."

A small knot of people gathered to look at it.

"I will go off in four hours, four minutes, and thirty-seven seconds."

A few people became worried as the bomb talked on. They remembered business elsewhere and hurried away, often toward the tube trains to King City. Eventually, the trains became overcrowded and there was some pushing and shoving.

The bomb was a metal cylinder, a meter high, two meters long, mounted on four steerable wheels. There was an array of four television cameras mounted on top of the cylinder, slowly scanning through ninety degrees. No one could recall how it came to be there. It looked a little like the municipal street-cleaning machines; perhaps no one had noticed it because of that.

"I am rated at fifty kilotons," the bomb said, with a trace of pride.

The police were called.

"A nuclear bomb, you say?" Municipal Police Chief Anna-Louise Bach felt sourness in the pit of her stomach and reached for a box of medicated candy. She was overdue for a new stomach, but the rate she went through them on her job coupled with the size of her paycheck had caused her to rely more and more on these stopgap measures. And the cost of cloned transplants was going up.

"It says fifty kilotons," said the man on the screen. "I don't see what else it could be. Unless it's just faking, of course. We're moving in radiation detectors."

"You said 'it says.' Are you speaking of a note, or phone call, or what?"

"No. It's talking to us. Seems friendly enough, too, but we haven't gotten around to asking it to disarm itself. It could be that its friendliness won't extend that far."

"No doubt." She ate another candy. "Call in the bomb squad, of course. Then tell them to do nothing until I arrive, other than look the situation over. I'm going to make a few calls, then I'll be there. No more than thirty minutes."

"All right. Will do."

There was nothing for it but to look for help. No nuclear bomb had ever been used on Luna. Bach had no experience with them, nor did her bomb crew. She brought her computer on line.

Roger Birkson liked his job. It wasn't so much the working conditions—which were appalling—but the fringe benefits. He was on call for thirty days, twenty-four hours a day, at a salary that was nearly astronomical. Then he got eleven months paid vacation. He was paid for the entire year whether or not he ever had to exercise his special talents during his thirty days duty. In that way, he was like a firefighter. In a way, he was a firefighter.

He spent his long vacations in Luna. No one had ever asked Birkson why he did so; had they asked, he would not have known. But the reason was a subconscious conviction that one day the entire planet Earth would blow up in one glorious fireball. He didn't want to be there when it happened.

Birkson's job was bomb disarming for the geopolitical administrative unit called CommEcon Europe. On a busy shift he might save the lives of twenty million CE Europeans.

Of the thirty-five Terran bomb experts vacationing on Luna at the time of the Leystrasse bomb scare, Birkson happened to be closest to the projected epicenter of the blast. The Central Computer found him twenty-five seconds after Chief Bach rang off from her initial report. He was lining up a putt on the seventeenth green of the Burning Tree underground golf course, a half kilometer from Prosperity Plaza, when his bag of clubs began to ring. Birkson was wealthy. He employed a human caddy instead of the mechanical sort. The caddy dropped the flag he had been holding and went to answer it. Birkson took a few practice swings, but found that his concentration had been broken. He relaxed, and took the call.

"I need your advice," Bach said, without preamble. "I'm the Chief of Municipal Police for New Dresden, Anna-Louise Bach. I've had a report on a nuclear bomb on the Leystrasse, and I don't have anyone with your experience in these matters. Could you meet me at the tube station in ten minutes?"

"Are you crazy? I'm shooting for a seventy-five with two holes to go, an easy three-footer on seventeen and facing a par five on the last hole, and you expect me to go chasing after a hoax?"

"Do you know it to be a hoax?" Bach asked, wishing he would say yes.

"Well, no, I just now heard about it, myself. But ninety percent of them are, you know."

"Fine. I suggest you continue your game. And since you're so sure, I'm going to have Burning Tree sealed off for the duration of the emergency. I want you right there."

Birkson considered this. "About how far away is this 'Leystrasse'?"

"About six hundred meters. Five levels up from you, and one sector over. Don't worry. There must be dozens of steel plates between you and the hoax. You just sit tight, all right?" Birkson said nothing.

"I'll be at the tube station in ten minutes," Bach said.

"I'll be in a special capsule. It'll be the last one for five hours." She hung up.

Birkson contemplated the wall of the underground enclosure. Then he knelt on the green and lined up his putt. He addressed the ball, tapped it, and heard the satisfying rattle as it sank into the cup.

He looked longingly at the eighteenth tee, then jogged off to the clubhouse.

"I'll be right back," he called over his shoulder.

Bach's capsule was two minutes late, but she had to wait another minute for Birkson to show up. She fumed, trying not to glance at the timepiece embedded in her wrist.

He got in, still carrying his putter, and their heads were jerked back as the capsule was launched. They moved for only a short distance, then came to a halt. The door didn't open.

"The system's probably tied up," Bach said, squirming. She didn't like to see the municipal services fail in the company of this Terran.

"Ah," Birkson said, flashing a grin with an impossible number of square teeth. "A panic evacuation, no doubt. You didn't have the tube system closed down, I suppose?"

"No," she said. "I... well, I thought there might be a chance to get a large number of people away from the area in case this thing does go off."

He shook his head, and grinned again. He put this grin after every sentence he spoke, like punctuation.

"You'd better seal off the city. If it's a hoax, you're going to have hundreds of dead and injured from the panic. It's a lost cause trying to evacuate. At most, you might save a few thousand."

"But..."

"Keep them stationary. If it goes off, it's no use anyway. You'll lose the whole city. And no one's going to question your judgment because you'll be dead. If it doesn't go off, you'll be sitting pretty for having prevented a panic. Do it. I know."

Bach began to really dislike this man right then, but decided to follow his advice. And his thinking did have a certain cold logic. She phoned the station and had the lid clamped on the city. Now the cars in the cross-tube ahead would be cleared, leaving only her priority capsule moving.

They used the few minutes delay while the order was implemented to size each other up. Bach saw a blonde, square-jawed young man in a checkered sweater and gold knickers. He had a friendly face, and that was what puzzled her. There was no trace of worry on his smooth features. His hands were steady, clasped calmly around the steel shaft of his putter. She wouldn't have called his manner cocky or assured, but he did manage to look cheerful.