"But what has all this to do with the canals?" I asked, my head still spinning, "And the Agreement?"

Gillian paused again, evidently formulating her words.

"Inevitably, social tensions grew in those ancient religious societies, leading to revolution and civil instability. Breakaway individuals strived for improvements in the lot of the common people - better conditions, more food - and of course increases in personal wealth. This led to the runaway development of resource-hungry engineering, allowing more leisure time and the time to develop more sophisticated technologies, and so on - a vicious circle which threatened to consume the entire world again, and again."

She sighed.

"We took a different approach. The dedication we apply to maintenance of the canals, and their extensions, and all the associated buildings, is analogous to the role that the building of churches and cathedrals had taken in those previous worlds. The purpose of the canals is to provide a sink for labour, a way of preventing idleness and sloth. And it is to give a visible result - a focus for pride and satisfaction in a job well done. But there is always, always more work to be done. It is a task for forever, a vital part of the success of the Agreement."

I thought about this. Of course, work on a canal could be slowed down or stopped for a season or a year, or even a generation, if other work was more pressing - a famine or flood, some emergency or contingency which consumed all available resources.

We sat quietly, both deep in private contemplation lit only by the flickering of the candlelight. The chill of the autumn evening crept into the room. The Mayor made no attempt to light the fire, which I could see already laid with logs and kindling in the fireplace on the far side of the office.

"The retrofitting of the world took generations," The Mayor eventually resumed, "Generations where people were encouraged to have very few children - ideally, none. This was the Age of the Lost Cohorts, generations where almost everybody was old. Some people even demonstrated their commitment to the Agreement by volunteering for euthanasia, rather than burdening the world with a need for medicines and help in their old age."

"Indeed some fanatics volunteered for tasks that were very dangerous - even fatal - reworking areas of the world poisoned by machines and industry. These volunteers knew they would die from the poisons, and undertook the tasks provided they could be assured of a quick and painless death afterwards; their reward being the knowledge that they have contributed to the long-term survival of the human species."

"Each generation used less and less technology, slowly establishing the way of living with which we are familiar, and carefully destroying - very thoroughly, we are told - both the technology itself and all records of how the machines were made."

"And so each generation had fewer people. As centres of population became untenable, people moved together, huddling, really, against an increasingly large and lonely planet, until the world, and the adult population, was ready for the Final Agreement."

Again she paused, looking directly at me with eyes that seemed somehow to pierce my very thoughts.

"Remember, at some point in our history, every adult in the world - and I mean everyone - would have had to lie to their offspring, to set up the system of beliefs that they knew to be artificial, false. In short, to put in place the society that we now know. Even one person failing to honour the Agreement could have wreaked havoc with the Grand Plan, could have sown the seeds of insurrection and have instigated exactly the kind of instability that we had striven over the generations to achieve. Even our system of dates is a lie," she concluded, "We actually achieved this stasis less than two hundred years ago."

"So what happened to this Final Agreement," I asked, my mind still racing at the revelations being put before me.

"Oh, it still exists," the Mayor said, smiling sadly at my confusion, "Part of the Agreement was that, in each centre of population there would be one or two people who knew the truth. Typically, they would be an older person and a younger person, each in a position of responsibility and, quite frankly, power. In our settlement, for some reason - it's not deliberate policy - more often than not the persons selected are women. And, right now, those two people are me, and you."

Again, I gasped, beginning to realise my part in all this.

"A key part of the Agreement is that, in each generation, the truth was explained, understood and, most importantly agreed to, for the next generation, It was there to allow those in the know the ability to make informed decisions, to understand just what the Agreement is, and why it is so important."

Just at that moment, there was a tapping on the window. I started, turning towards the source of the noise. Gillian stood, raising a hand in reassurance.

"Ah," she said, "My other visitor this evening."

The Mayor undid the latch, allowing the window to slide open, then stepped back from the aperture. A sinuous figure slipped inside, moved swiftly to the centre of the room as if it wished to keep plenty of space between itself and the other occupants. The newcomer brought with it a damp smell, faintly unpleasant but somehow familiar, which after a few moments I recognised as that of water from the canals.

The creature stood upright, standing perhaps five feet tall, dripping water onto the stone flags of the floor. It was one of the Webbed Ones. In the candlelight, I could see the overlarge webbed hands and feet, the mottled brown and green skin with the slight suggestion of scales. It regarded me with its mobile and faintly luminous eyes.

"Good evening," it said politely, lisping very slightly through its lipless mouth, "Call me Snake."

I must have been sitting immobile, shocked by the appearance of this mythical figure in the quiet room.

"So you are to be the new Mayor?" Snake continued, pacing to one side and then the other, looking me over appraisingly.

Finally, the Webbed One stopped, still keeping its distance from myself and the Mayor.

"I think you will do well enough," it continued, "I know you. I have been watching you for some time. I saw you on the bank of the canal earlier today" - I gasped - "I apologise for any alarm I may have caused."

I could contain myself no longer.

"Snake, what are you?" I burst out.

The creature emitted a series of hissing puffs which I took to be its laughter.

"Our people are an even more extreme human survival strategy - one of several, I should say," Snake said, "We were once as you. But we were modified, engineered, by the vanished science of the Ancients, to a kind that can live in and out of water, a kind that did not need even the limited technologies you permit yourselves. A different approach to human survival, in case the world changed in ways unforeseen even by the Old Ones."

I stared at it - him? her? - incredulously. He twisted his lips curiously, showing numerous sharp yellow teeth.

"There are other groups, all over this world, some not so far from here," he continued, "Some are peoples like yourselves, basic humans. Others are adaptations such as ourselves, one of a myriad of kinds in shapes you cannot even imagine."

Snake laughed again.

"We call you 'the mice'," he said, "Living quietly, timidly in your houses and windmills, busying yourselves with your canals."

"Why are you here?" I demanded, "I mean, in this room, at this time?"

Again, the Webbed One displayed that twisting of the lips, and I was forced to conclude that the creature was smiling.

"I am a witness," he said slowly, with a serious tone at odds with the facial expression, "To the continuing Agreement. The leaders of our kind - I am their representative - wish the Agreement to continue. And I am here, tonight, to hear from you in person your commitment to its continuation."

I now understood the temptation, and the danger, embodied in the Agreement. Of course, I could not change things overnight. Even if I ran outside right now, shouting the truth to the four winds, I would not be believed. I would be considered mad, or possessed; I would be feared or pitied, or incarcerated for my own protection.

But I could be more subtle, particularly with the influence of the Mayor behind me - or even as Mayor. I could put in place changes which would change our society. I could order a slowdown - or a complete stop - of the works on the canals and the associated buildings. Instead, I could encourage the building of ships, to travel the outer world, and send out explorers - and traders, too, now that I understood that there were more groups of humans on this planet than I had known. I could arrange that the brightest of people could have leisure time to think, and more schooling and education to give the intellectual tools with which to do it.

And, most importantly, I could suppress all knowledge of the Agreement, and the lies that our histories are. With that impetus of belief, I could engineer the re-birth of a technological society that could, in a few generations - perhaps only ten or twenty - build the machines that could take us to the stars.

Or, I could decide to leave things as they were, unchanged until the next millennium.

I stood slowly, understanding the formality of the moment.

"The Agreement stands," I said slowly and clearly, "Unto the next generation."

Snake and the Mayor nodded their approval in strange synchronisation. Then, without another word, the creature turned on its tail and slipped out of the open window as quickly and quietly as he had come. Gillian shut the window behind the vanished Snake, and bent to light the fire.

Part 3 Afterword