Lauren Stansfield was a tougher challenge. The woman presented herself as the very model of Ms. Cool, but occasionally, as when John had interrupted her assertion of theft, you sensed a spark of fire inside the ice.

Since Lauren was taking over John Hyslop’s duties, she must be highly competent. That came across in her demeanor. Otherwise, she was an invisible woman. Maddy had the feeling that if she turned her back on Lauren, the woman would fade from view within seconds.

No one is calm, no one is logical. Inside, everybody is a volcano. That was Gordy Rolfe’s guiding principle, the one he had used to build the Argos Group.

It worked fine down on Earth — brawling, selfish, tormented Earth. But what about here, in the quiet sanctuary of Sky City, with its abundance of calm and logical engineers? Maybe Gordy’s principle didn’t work at all.

Maddy turned away from John and Lauren, still deep in their number swapping, and looked out along the great length of the communal hall.

Everything was peaceful. Calm, logic, order, rational behavior made manifest. But someone on Sky City, perhaps one of the very people she was now watching, was an insane murderer.

Underneath, even here, burned the volcano.

interlude 2

interlude: Sniffer, Model B.

Two years in the million-year evolution of human intelligence is nothing, less than an eyeblink. Two years in the twenty-first-century development of machine intelligence is a significant interval.

In outward appearance and even in internal hardware, Sniffer-A and Sniffer-B were almost identical, but the second model possessed a far higher degree of program flexibility. In human terms it was still no more than a low-grade moron with unique specialized talents, a silicon-based idiot savant, but it was enormously smarter than Sniffer-A. Model B could correlate predicted and observed values, decide if the difference between the two was significant, and then — a major improvement — vary the performance of its onboard sensors and analytical tools.

The Sniffer tasted the speeding front of the particle flux and decided, as Sniffer-A had done two years earlier, that the difference from expectations went far beyond statistical tolerance. That result was sent on its light-speed journey back to Earth, while at the same time a new sampling protocol was introduced. The arrival times of the anomalously heavy particle nuclei were measurable to within an attosecond. Even moving at an appreciable fraction of light speed, nucleic separation distances of less than an atomic diameter could be determined.

The Sniffer was well equipped to analyze time series data. It was clear that the arrival times of groups of nuclei of different species were tightly correlated. Those groups were also very large, usually containing trillions of separate nuclei. The time pattern was seldom repeated, but the number of a particular type of nucleus contained within a single cluster was usually the same.

Sniffer-B pondered the problem at a thousand billion cycles a second as it flew on through the incident flux. It held in its general data base enough information to realize that the external world was not composed of one-dimensional entities. The data series that it was observing was a projection onto a single dimension — time — of three-dimensional structures. The Sniffer also had information on organic chemistry, enough to infer how a complex structure, such as a molecule, would appear if projected onto any given axis in space. Varying the axis of projection would give patterns characteristic of the molecule, patterns that looked different from each other but in which the number of a particular kind of atom would always be the same.

The Sniffer struggled with the problem of reconstructing the spatial configuration of the clusters that its sensors were observing. It made the working assumption that the structure was always the same, but might be arriving at the sensors at any angle.

Sniffer-B tried, and tried, and failed. It knew that it needed a method for the inference of spatial structures applicable to the clusters of nuclei, but the closest relevant technique — the theory of molecular crystallography — had seemed to the Sniffer’s makers far beyond the set of applications likely to be useful in the interstellar environment.

The Sniffer did not know how to stop trying. It continued with its ceaseless ferment of computation long after the main flux of particles had passed. Only when all systems were powered down for the long interstellar cruise did the analysis process suspend.

It would start up again one more time, when arrival at Alpha Centauri triggered a last flurry of futile activity. The Sniffer would never know that the puzzle racking its circuits had been solved, within days of its receipt on Earth, by the slow and inefficient organic computers of its makers.

Nick Lopez was waiting for Celine when Suborbital One touched down at the New Rio port. As they taxied in she saw him waiting on the tarmac. His broad, simple face and warm, welcoming smile made her think, not for the first time, I’m the President, but he’s the politician.

How could you dislike somebody so cheerful and so positive? How could you resist that sunny smile? When you were with him, you couldn’t. Only when you went away and read the thirty-year catalog of suspicions and rumors and unsuccessful charges against him did the doubts come back.

“Good flight, Madam President?” He engulfed her hand in his warm brown paw as she reached the bottom of the glide stair, and grinned down at her from his thirty-centimeter height advantage.

Celine shrugged. The plane had squeaked in under the nose of a July storm racing in from the northwest, and during the final approach a bout of turbulence had been too much for the stabilizers. “You know what they say — if you can walk away from a landing, it was a good flight. Actually, I’ve known better. But we had to do our final approach from the south because of the weather. And I wondered, are those new beaches that I saw?”

“Under construction.” Nick fell into step beside her. “New beaches, but with the old names. Copacabana, Ipanema, Leblon, Gavea. Don’t you just love them, the dreams from the past? Though of course, I don’t plan to visit the new beaches; they’re for the younger generation.”

Celine was not so sure. Nick’s file was a thick one. Long before the supernova, U.S. Senator Nick Lopez had been a frequent visitor to the Rio de Janeiro beaches. He had not been above bringing his young male pickups back to Washington and showing them off around the halls of Congress. Now he wore his trademark hairstyle, a shaped high pompadour, deliberately gray, but he was in excellent physical shape. It would be no surprise if he still followed his old habits. It was Nick, after all, who had decided that the main headquarters for the World Protection Federation would be in New Rio.

Still, no one could argue with his logic. New Rio had space available, and lots of it. The old line “And I alone lived on to tell the tale” applied literally to Joachim Salazar, an inhabitant of the old city of Rio de Janeiro. After the supernova, rain had fallen continuously and torrentially in the Serra dos Orgaos, the mountains to the west of Rio; rain from March 2 to September 5, one hundred and eighty-eight days and nights. At the end of that time the city was gone. The great bridge across the harbor had been riven from its supports and lay on the bed of Guanabara Bay. The airport on Ilha do Governador had disappeared, along with the island itself. The famous beaches south of Rio, Copacabana and Ipanema and the others, had vanished.

So had Rio’s seven million residents. The post-supernova surveys found no trace of them. Only Joachim Salazar survived. Huddled inside an inverted mobile home, he had washed out to sea on a vast slurry of mud and water surging into the Atlantic between Sugarloaf Mountain and the Parrot’s Beak promontory. He had floated in the open ocean for thirty-nine days and been picked up, dehydrated and demented, six hundred miles out to sea. Salazar’s memories, such as they were, provided the only record of the last days of Rio.