“You mean, in the chapels? Never interested me.”

“It might help you. It won’t cure what you have, but it might make it easier for you to live with it. Carpentry shows you patterns that you can’t necessarily see for yourself. It helps you sort what’s real and important from what doesn’t matter much.”

“So you’re a carpentry nut?”

“I go now and then. Whenever things cut too close. There are some chapels down by Fisherman’s Wharf. I wouldn’t mind going now. Suppose you come down there with me. It’ll do you some good.”

“There’s a bar at Washington and Stockton that I go to a lot. Suppose we go there instead. Suppose you buy me some drinks on your PRC card. Do me even more good,”

“Bar first, then chapel?”

“We’ll see,” Ehrenreich says.

The bar is dark, musty, a forlorn place. The bartender is an automatic: card in slot, thumb to identification plate, punch for drinks. They order martinis. Ehrenreich’s truculence subsides after his second drink; he grows morose and maudlin, but he is less bitter now. “I’m sorry I said what I did, man,” he multers.

“Forget it.”

“I really thought you’d be the one.”

“I wish I could be.”

“I don’t wish any trouble on you.”

“I’m in trouble already,” Shadrach says. “Hanging on by my fingernails.” He laughs. A new round of drinks comes from the machine. He lifts his glass. “Never mind. Cheers, friend.”

“Cheers, man.”

“After this one we’ll go to the chapel, right?”

Ehrenreich shakes his head. “Not me. It’s not for me, you know? Not now. Not right now. You go without me. Don’t nag me about it, just go without me.”

“All right,” Shadrach says.

He finishes his drink, touches Ehrenreich’s arm lightly in farewell — the man is glassy-eyed, inarticulate — and finds a cab to take him down to the Wharf. But the chapel gives Shadrach no ease today. His fingers tremble, his eyes will not focus, he is unable to slip into the meditative state. After half an hour he leaves. He sees a car full of Citpols in a lot up the block. They’re still watching him. There is a bearded man in street clothes in the car, also. Ehrenreich? Is that possible? At this distance he can’t make out faces, but the heavy shoulders look about right, the thinning hair is familiar. Shadrach scowls. He hails a taxi, goes back to his hotel, packs, heads for the airport. Three hours later he is on his way to Peking.

In Peking, ensconced at the Hundred Gates Hotel in the old legation quarter adjoining the Forbidden City district, where Kublai Khan and Ch’ien-lung once held court, Shadrach begins once more to detect emanations from Genghis Mao. He is still some twelve hundred or thirteen hundred kilometers from Ulan Bator, he calculates — beyond the optimum telemetering range, and so the incoming impulses are blurred and faint. Then, too, after these weeks of separation Shadrach is no longer as much in concord with the broadcast from Genghis Mao’s body as he had been. But when he sits very still, when he tunes his attention perfectly to the task, he finds himself able to read the old warlord’s biodata with gradually sharpening clarity.

The gross functions come in best, of course: heartbeat, blood pressure, respiration, body temperature. The Khan’s major systems all seem to be thundering along at their usual level of irrepressible vitality. Liver and kidney action register in their normal range. Basal metabolic expenditure normal. Neuromus-cular responses normal. It never ceases to amaze Shadrach how healthy, how strong, the old man is. He takes a certain vicarious pride in Genghis Mao’s heroic durability and resilience. Some unexpected puzzles begin to develop, though, as Shadrach extends his reach and starts to bring in the subtler, more refined data. These tend to contradict some of the gross indications. The muscle-firing responses do not seem quite right — phosphate breakdown appears weak, enzyme activity off. Blood viscosity is lower than normal and blood pH is nudging slightly toward the alkaline. Intestinal absorption is minutely down, cholesterol accumulation up, perspiration a trifle above normal. None of these things is cause for real alarm in a man of the Chairman’s age who has recently undergone so much radical surgery — it is hardly reasonable to expect htm to be in perfect health — but the combination of factors is peculiar. Shadrach wonders how much of what he is reading is simply an artifact of distance and noise on the line: he is straining for some of these inputs, and he may not be getting them accurately. Still, the distortions, if distortions they are, are remarkably consistent. He gets the same reading whenever he returns to any sensor.

And a hypothesis is starling to take shape.

Diagnosis at more than a thousand kilometers’ range is tricky. Shadrach misses his medical library and his computers. But he has an idea of what the problem may be, and he knows what data he needs to confirm his theory. What he does not know is whether Buckmaster’s implant system is good enough to transmit analogues of such small-scale phenomena across so great a distance.

If blood viscosity is down and blood pH is alkaline, plasma protein levels are probably subnormal, and osmotic pressure, which draws fluids from the tissues to the capillaries, is going to be low. If the hydrostatic blood pressure is normal, as the gross function modulator is telling him, and the osmotic blood pressure is off, Genghis Mao’s tissues may be building up an accumulation of excess fluids — not serious, not dangerous, not yet, but such fluid accumulations may be leading toward the development of edemas, of watery swellings, and edemas can be symptomatic of impending failure in the kidneys, the liver, perhaps the cardiac system. Bearing down in intense concentration, Shadrach roves Genghis Mao’s body in search of signs of excess fluid. The lymphatic-system checkpoints give him nothing but normal levels, though. The reports from the pericardial, pleural, and peritoneal outposts are positive. Renal and hepatic functions, as before, are fine. Nothing seems to be wrong. Shadrach begins to abandon his hypothesis. Perhaps the Khan is not in difficulties. Those few negative indications were probably just noise on the line, and therefore—

But then Shadrach notices that something is not quite right in Genghis Mao’s skull. Intracranial pressure is unusually high.

The implant monitors in the Chairman’s cranium are not as comprehensive as they are elsewhere. Genghis Mao has no history of stroke or other cerebrovascular events, and surgeons have never had reason to invade the imperial skull. Since most of the telemetering equipment in Genghis Mao has been installed during the course of routine corrective surgery, Shadrach must make do with relatively skimpy coverage of the state of the Chairman’s brain. But he does have a sensor that reports to him on intracranial pressure, and, as he makes his total scan of Genghis Mao’s body, the rise in that pressure catches his attention. Is that where the fluid buildup is taking place?

Struggling, stretching for the data, Shadrach pulls in whatever correlative information he can grab. Osmotic pressure of the cranial capillaries? Low. Hydrostatic pressure? Normal. Meningeal distension? High. Condition of the cerebral ventricles? Congested. Something is awry, very marginally awry, in the system that drains cerebrospinal fluid from the interior of Genghis Mao’s brain to the subarachnoid space, next to the skull wall, whereit normally passes into the blood.

What this means, at the moment, is that Genghis Mao probably has been having bad headaches for a few days, that he will have worse ones if Shadrach Mordecai does not return to Ulan Bator at once, and that he may suffer brain damage — possibly fatal — if prompt corrective action is not taken. It means, also, that Shadrach’s holiday is at its end. He will not do the sightseeing tour of Peking. Not for him the visit to the Forbidden City, the historical museum, the Ming tombs, the Great Wall, the temple of Confucius, the Working People’s Palace of Culture. Those things are unimportant to him now: this is the moment for which he was waiting during his wanderings from continent to continent. The unstable system that is Genghis II Mao IV Khan has, in the absence of the devoted physician, begun to break down. Shadrach’s indispensability has been made manifest. He is needed. He must go to his patient immediately. He must take the appropriate actions. He has his Hippocratic obligations to fulfill. He has his own survival to think about, besides.