And the woman plucks at his sleeve, and he sees that she is Katya, and he says, “What do you want?” She says, It’s too late. He says, “The next donor’s already been picked?” Yes. “I don’t suppose you’d care to tell me his name.” I don’t think! should. “Who is he?” You, she says.The world erupts in flame and flood. The laughter of Genghis Mao rolls through the heavens, shattering mountains. Shadrach awakens. He sits up. He clenches his fist and holds it tightly clenched. Out of Ulan Bator, four hundred kilometers to the east, comes the terrible jolt of Genghis Mao’s agony, the silent scream of the sensors reporiing the wave of pain that is sweeping through the Khan.

Shadrach approaches Interface Three and announces, “Shadrach Mordecai to serve the Khan.”

He is scanned. He is approved. He is admitted.

It is close to midnight. Shadrach goes at once to the Khan’s bedroom, but Genghis Mao is not there. Shadrach frowns. The Khan has been strong enough to leave his bed for the past several days, but it is odd that he should be wandering around this late at night. Shadrach finds a servitor who tells him that the Khan has spent most of the evening in the secluded study known as the Khan’s Retreat, on the far side of the seventy-five-story compound, and is probably there now.

Onward, then. Into the Khan’s office — he is not there — and thence to the private imperial dining room, empty, and then Shadrach goes into his own office, where he pauses a moment, collecting himself amid his familiar and beloved possessions, his sphygmomanometers and scalpels, his microtomes and trephines. Here, in a flask, is the authentic abdominal aorta of Genghis II Mao IV Khan. Surely a treasure of medical history, that one. And here, the newest addition to Shadrach’s museum, is a lock of Genghis Mao’s thick, rank, preternaturally dark hair, an exhibit perhaps more fitting for a museum of witchcraft and voodoo than one of medicine, but yet appropriate, for it was removed in the course of preparations for brain surgery carried out successfully in the celebrated patient’s ninetieth (or eighty-fifth, or ninety-fifth, or whatever) year of life. And so. Onward. He presents himself to the door of the Khan’s Retreat and asks entry.

The door rolls back.

The Khan’s Retreat is the room least used on the floor, accessible only through Shadrach’s office and insulated against the intrusion of even the loudest external distractions. Its ceiling is low, its lights are dim, its furnishings are ornate and oriental, running toward thick draperies and elaborate carpets. Genghis Mao lies on a cushioned divan along the left-hand wall. Already his shaven scalp is coveted by a thin black stubble. The vitality of the man is irrepressible. But he looks shaken, even dazed.

“Shadrach,” he says. His voice is thick and scratchy. “I knew you’d get here. You felt it, didn’t you? About an hour and a half ago. I thought my head was going to explode.”

“I felt it, yes.”

“You told me you were putting a valve in me. To drain off the fluid, you said.”

“We did, sir.”

“Doesn’t it work right?”

“It works perfectly, sir,” Shadrach says mildly.

Genghis Mao looks confused. “Then what made my head hurt so much a litlle while ago?”

“This did,” says Shadrach. He smiles and stretches forth his left hand and clenches his fist.

For a moment nothing happens. Then Genghis Mao’s eyes widen in shock and amazement. He growls and clamps his hands to his temples. He bites his lip, he bows his naked head, he drives his knuckles against his eyes, he mutters anguished guttural curses. The implanted sensors that report on the bodily functions of the Khan tell Shadrach of the intense reactions within Genghis Mao: pulse and respiration rates climbing alarmingly, blood pressure dropping, intracranial pressure severe. Genghis Mao coils into a huddled ball, shivering, groaning. Shadrach lets his fingers relax. Gradually the pain recedes from Genghis Mao, the tense crumpled body uncoils, and Shadrach ceases to feel the broadcast of shock symptoms. Genghis Mao looks up. He stares at Shadrach for a long moment.

“What have you done to me?” Genghis Mao asks in a harsh whisper.

“Installed a valve in your skull, sir. To drain away the dangerous accumulations of cerebrospinal fluid. However, I should tell you that the action of the valve has been designed to be reversible. Upon telemetered command it can be made to pump fluid into the cranial ventricles instead of draining it from them. I control the action of the valve, here, by a piezoelectric crystal implanted in my palm. A twitch of my hand and the fluid ceases to drain. A harder twitch and I can pump it upward. I can interrupt your life processes. I can cause you instant pain of the kind you have now experienced twice, and in a surprisingly short span of time I could cause your death.”

Genghis Mao’s facial expression is entirely opaque. He considers Shadrach’s declaration in silence.

Eventually he says, “Why have you done this to me, Shadrach?”

“To protect myself, sir.” The Khan manages a glacial smile. “You thought I would use your body for Project Avatar?”

“I was certain of it, sir.”

“Wrong. It wouldn’t ever have happened. You’re too important for me as you are, Shadrach.”

“Yes, sir. Thank you, sir.”

“You think I’m lying. I tell you that there was never any possibility we would have activated Project Avatar with you as the donor. Don’t misunderstand me, Shadrach. I’m not pleading with you now. I’m simply telling you how things really stand.”

“Yes, sir. But I know your teachings concerning redundancy, sir. I feared I was about to be made dispensable, I have made myself indispensable now, I think.”

“Would you kill me?” Genghis Mao asks.

“If I felt my life was in danger, yes.”

“What would Hippocrates say about that?”

“The right of self defense is allowed even to physicians, sir.”

Genghis Mao’s smile grows warmer. He seems to be enjoying this discussion. There is no trace of anger on his face.

He says calmly, merely raising a speculative hypothesis, “Suppose I have you seized by stealth, immobilized before you can clench your fist, and put to death?”

Shadrach shakes his head, “The implant in my hand is keyed to the electrical output of my brain. If I die, if I’m mindpicked in any way, if there’s any sort of significant interruption in my brain waves, the valve automatically begins pumping cerebro-spinal fluid to your medulla. The moment of my death is the automatic prelude to your own, sir. Our fates are joined. Guard my life, sir, for your own sake.”

“And if I have the valve removed from my head and replaced by one that isn’t quite as — ah — versatile?”

“No, sir. There’s no way you could enter surgery without my implant system notifying me of it. I’d take defensive action, naturally, at the first moment. No. We have become one entity in two bodies, sir. And we’ll remain that way forever.”

“Very clever. Who built this mechanical marvel for you?”

“Buckmaster did, sir.”

“Buckmaster? But he’s been dead since May. You couldn’t have known then—”

“Buckmaster is still alive, sir,” Shadrach says softly.

Genghis Mao considers that. He grows extremely thoughtful. He is silent for a long while. “Still alive. Strange.”

“Yes.”

“I don’t understand. ” Shadrach makes no reply. After a time Genghis Mao says, “You’ve planted a bomb in me.”

“So to speak, sir, I have.”

“I have power over all of mankind. And you have power over me, Shadrach. Do you realize what that makes you? You are the true Khan now! All hail, Genghis III Mao V!” Genghis Mao laughs savagely. “Do you understand that? Do you know what you have achieved?”

“The thought has crossed my mind,” Shadrach admits.

“You could force my resignation. You could compel me to name you as my successor. You could kill me and assume the Chairmanship, perfectly legitimately. You see that? Of course you see that. Is that what you mean to do?”