Beyond that, I can’t say for certain just what had happened. But in the years that followed, I certainly speculated. I wondered if perhaps only an inner circle of the cult had known about the grand plan to wipe out humanity. And, once the deed had been irrevocably done, perhaps all they needed to do, to keep the rest of the cultists in line, was to threaten to withhold the antidote.

But their leaders were few, and their followers many. Once the promised paradise on Earth failed to materialize, that controlling minority – I felt increasingly certain – must have been faced with overwhelming opposition to their rule. And if those smashed ampoules were anything to judge by, those in charge must have been just as petty and venal as the billions they had sentenced to death. It looked as if they had destroyed the remaining supplies of the antidote rather than allow the rebels to seize it.

With the existing supplies of the antidote destroyed, how was I, then, to survive?

I found a place to sleep in a deserted dormitory within the compound, then spent the next several days looking for anything that might possibly help me survive longer than the next few months. Eventually I found a well-equipped laboratory, but most of the equipment had either been smashed to pieces or burned. This at least explained why the rebels had been unable to synthesize any more antidote themselves.

It took another week of searching, but finally I discovered an unharmed cache of the antidote. It was hidden in a crate at the back of a barn on the very edge of the property, along with lab workbooks detailing the requisite formulae to synthesize more.

I soon formulated a plan that would give me purpose in the coming years. First, I would search for other survivors, if they were out there. Somewhere in the world, there had to be secure facilities with people surviving on canned air, or in underground military complexes built to withstand nuclear or biological attack.

I was telling myself a lie, of course: one that gave me a reason to hold my grief and anger at bay, not to mention the dreadful guilt I felt at the thought that I could have found some way to escape sooner, to warn people of what was happening. Sometimes, the grief gave way to anger, and in my mind I called myself a coward.

Still the tenacious will to live that had spurred me this far refused to let go, and before long I was back on the road, making my way across the vastness of the North American continent. Over the next three years I criss-crossed from coast to coast, and found nothing but deserted ruins slowly reverting to nature. At some point I found another yacht and sailed it back across the ocean.