Still, his equations held. In terror of hubris, Isaac sought any alternative than to believe what was looking more and more like the truth: that he had solved the problem of mathematic representation, quantification, of crisis energy.

He knew that he should immediately converse with colleagues, publish his findings as “work in progress” in The Review of Philosophical Physics and Thaumaturgy, or the Unified Field. But he was so intimidated by what he had discovered that he avoided that route. He wanted to be sure, he told himself. He had to take a few more days, a few more weeks, maybe a month or two…then he would publish. He did not tell Lublamai or David, or Lin, which was more extraordinary. Isaac was a garrulous man, prone to spouting any old tosh, scientific, social or obscene, which came to his mind. His secretiveness was profoundly out of character. He knew himself well enough to recognize this, and to realize what it meant: he was deeply disturbed, and deeply, deeply excited by what he had found.

Isaac thought back on the process of discovery, of formulation. He realized that his advances, his incredible leaps of theory in the last month, which eclipsed his previous five years’ work, were all in response to immediate, practical concerns. He had reached an impasse in his studies of crisis theory until Yagharek had commissioned him. Isaac did not know why it was so, but he realized that it was with applications in mind that his most abstract theories were advancing. Accordingly, he decided not to immerse himself totally in abstruse theory. He would continue to focus on the problem of Yagharek’s flight.

He would not let himself think about the ramifications of his research, not at this stage. Everything he uncovered, every advance, every idea he had, he would quietly plough back into his applied studies. He tried to see everything as a means to get Yagharek back in the air. It was difficult-perverse, even-constantly trying to contain and circumscribe his work. He saw the situation as one of working behind his own back, or more exactly, as trying to do research out of the corner of his eye. Yet, incredible as it seemed, with the discipline that was forced on him, Isaac progressed theoretically at a rate he could never have dreamed of six months before.

It was an extraordinary, circuitous route to scientific revolution, he thought sometimes, chiding himself quickly for his direct gaze at the theory. Get back to work, he would tell himself sternly. There’s a garuda to get airborne. But he could not stop his heart from thumping with excitement, the occasional almost hysterical grin from racing across his face. Some days he sought Lin out and, if she was not working at her secret piece in her secret location, he would try to seduce her in her flat with a tender, excited fervour that delighted her, for all that she was obviously tired. At other times he spent days in only his own company, immersing himself in science.

Isaac applied his extraordinary insights and began tentatively to design a machine to solve Yagharek’s problem. The same drawing began to appear more and more in his work. At first it was a doodle, a few loosely connecting lines covered in arrows and question marks. Within days it was appearing more solid. Its lines were drawn in ruled ink. Its curves were measured and careful. It was on its way to becoming a blueprint.

Yagharek sometimes came back to Isaac’s laboratory, always when the two of them were alone. Isaac would hear the door creak open at night, turn to see the impassive, dignified garuda still steeped in visible misery.

Isaac found that trying to explain his work to Yagharek helped him. Not the big theoretical stuff, of course, but the applied science which furthered the half-hidden theory. Isaac spent days with a thousand ideas and potential projects swilling violently in his head, and to pare that down, to explain in non-technical language the various techniques he thought might enable him to tap crisis energy forced him to evaluate his trajectories, discard some, focus on others.

He began to rely on Yagharek’s interest. If too many days passed without the garuda appearing, Isaac became distracted. He spent those hours watching the enormous caterpillar.

The creature had gorged itself on dreamshit for nearly a fortnight, growing and growing. When it had reached three feet in length, Isaac had nervously stopped feeding it. Its cage was getting much too small. That would have to be the full extent of its size. It had spent the next day or two wandering around hopefully in its little space, waving its nose in the air. Since then it seemed to have resigned itself to the fact that it would get no more food. Its original desperate hunger had subsided.

It was not moving very much, just shifting around now and then, undulating once or twice the width of the cage, stretching as if yawning. For the most part it just sat and pulsed slightly in and out, with breath or heartbeat or what, Isaac did not know. It looked healthy enough. It looked as if it was waiting.

Sometimes, as he had dropped the gobs of dreamshit into the caterpillar’s eager mandibles, Isaac had found himself reflecting on his own experience with the drug with a faint, querulous longing. This was not the delusion of nostalgia. Isaac vividly remembered the sense of being awash in filth; of being sullied at the most profound level; the nauseating, disorientating sickness; the panicked confusion of losing himself in a welter of emotion, and losing the confusion, and mistaking it for another mind’s invading fears…And yet, despite the vehemence of those recollections, he found himself eyeing his caterpillar’s breakfasts with a speculative air-perhaps even a hungry one.

Isaac was very disturbed by these feelings. He had always been unashamedly cowardly when it came to drugs. As a student, there had been plenty of loose, smelly fogweed cigarillos, of course, and the inane giggles that went with that. But Isaac had never had the stomach for anything stronger. These inchoate rumblings of a new appetite did nothing to allay his fears. He did not know how addictive dreamshit was, if at all, but he sternly refused to give in to those faint stirrings of curiosity.

The dreamshit was for his caterpillar, and for it alone.

Isaac channelled his curiosity from sensual into intellectual currents. He knew only two chymists personally, both unutterable prudes with whom he would no more raise the question of illegal drugs than he would dance naked down the middle of Tervisadd Way. Instead, he raised the subject of dreamshit in the louche taverns of Salacus Fields. Several of his acquaintances turned out to have sampled the drug, and a few were regular users.

Dreamshit did not seem to differ in effect between the races. No one knew where the drug came from, but all who admitted to taking it sang paeans of praise to its extraordinary effects. The only thing they all agreed on was that dreamshit was expensive, and getting more so. Not that this put them off their habits. The artists in particular spoke in quasi-mystical terms of communing with other minds. Isaac scoffed at this, claiming (without acknowledging his own limited experience) that the drug was no more than a powerful oneirogen, that stimulated the dream-centres of the brain as very-tea stimulated the visual and olfactory cortexes.

He did not believe it himself. He was not surprised at the vehement opposition to his theory.

“I don’t know how, ‘Zaac,” Thighs Growing had hissed at him reverentially, “but it lets you share dreams…” At this, the other users crammed into a little booth in The Clock and Cockerel had nodded in time, comically. Isaac affected a sceptical face, to maintain his role of killjoy. Actually, of course, he agreed. He intended to find out more about the extraordinary substance-Lemuel Pigeon would be the person to ask, or Lucky Gazid, if he ever reappeared-but the pace of his work in crisis theory overtook him. His attitude to the dreamshit he had shoved into the grub’s cage remained one of curiosity, nervousness and ignorance.