At the height of the 1918 influenza epidemic, the curling stink of death was inescapable. It hung thick as damp blankets in homes, where virtually every family watched helplessly as some of their loved ones died. Out in the autumn streets, you caught sudden and stunning smells of the newly dead as stricken homes brought their corpses out to meet the public health patrols. Charged with picking up and disposing of hundreds of bodies, the patrols were comprised of police officers, exhausted from the endless days of double duty, with puffy eyes showing over their cloth face masks. Sometimes one would fall, feverish and heaving, as he carried a corpse from a porch to the waiting wagon, and be unable to stand again. The smell of sickness, like fear, was everywhere. It got into your clothes, on your hands. In the offices and factories, where one-third of the workforce might not show up on any given day, people jumped at the sound of a cough. Without any warning, your body could become a fearsome time bomb. The disease was everywhere, and some called it Judgment.

It was easy to believe, in those years when the world blistered with war, that this lowly disease was an agent of God's disgust at the human race. The Great War stunned the human race, shattered a common dream that the twentieth century might bring forth a revolution in human existence. The glorious new technology of the age, having promised humanity a better life, was proving to be equally capable of destroying it. In the bloodwet mud trenches of Europe, young men were unearthing a stupefying vision of the New World. They were looking directly into the bright-hot muzzle of the future, and it was blowing off chunks of their bodies and minds.

Now the world seemed cloaked in disease. It was God's will, His judgment on a ferocious band of wayward children who had matched their potential for evil against His near-infinite capacity for mercy, and demonstrated their unworthiness. Now God was finishing what humankind was not yet able to do for themselves. His agent of destruction was nothing more than a microbe, an invisible, unbeatable enemy so small as to be sewn into the fabric of the world itself.

Terrified of catching the illness scouring their communities, people seldom left their houses. Churches were abandoned, theaters and schools closed.

In this climate of fear and disillusionment, Doomsday cults sprang up among otherwise common citizens. Among them were the Algorithmic Theologists, a Baltimore-based group led by chemist and physicist Alfred Mullen. His book On the Recrystallization of Eden postulates that when humanity first fell from grace and was expelled from Eden, we began a process of spiritual decay that continues today. Mullen compared this to the progressive breakdown of crystalline structures in certain solids when they are exposed to powerful solvents.

The Algorithmic Theologists were a loose band of scientists and pseudo-scientists who saw in Mullen's work the promise of a rational explanation for the catastrophes razing their world. Mullen believed that humankind continues to fall ever further from divine grace, at a pace which can be determined through mathematics.The group hoped to determine this complex formula through a rigorous analysis of theological texts from throughout the modern ages, based on a mathematical quantification of human behavior. It was believed that if humankind could determine the formula which accounted for our progressive estrangement from God, we could reverse the process. Neutralizing the corrosive solvents which caused our spiritual breakdown, we would begin to re-form and eventually reach the single crystalline purity of Eden.

Alfred Mullen's son sits across from me on the train. He has a copy of Mullen's book, bound in grubby leather. He is stooped, brittle, slouching over a paunchy belly that spreads the gaps between his shirt buttons and exposes a white t-shirt beneath. Hazy sodium lights fly by the windows, momentary novas in celestial clouds of flying insects. We glimpse a junkyard, jagged shells of wrecked cars torn open and cannibalized like old ideas.

"My father believed that the world could never survive another catastrophe like the Great War, World War I," he tells me in cracked cathedral tones. "He and those others, those other scientists, thought the world's decay was algorithmic. The longer things were left alone, the worse things got. The rate of decay got faster. They thought we were accelerating towards the end of the world and it was a race against time to find out an answer, a way to reverse this... to get us back on the track to Eden."

I had work to do on the train, but I've done none of it. I've spent two hours listening to this man, watching him idly flip through the old book that he apparently carries with him at all times, a charm against the terrifying future seen so clearly by those in our past.

What did you think of your father's work?

"I didn't have much to do with it," he says dismissively. I assume by this he means he never cared for it. He was the forth child of Mullen's third wife. He says that after the Influenza epidemic ended, most of Mullen's followers went on to other faiths and diversions. Without a flock to follow him, and perhaps to moderate his extreme beliefs, Mullen grew more eccentric. He ended his life penniless, dismissed from all the professorial posts that had once funded his extravagant theological research.

"It's too bad," the man says, "because I think he may have almost hit on something. I've always felt that." He thumps the book. Bright lights, the outskirts of a town, slide by us, and the door between train cars opens with a flatulent rush.

His father's mistake, his son says, is supposing that there was a point at which things could get no worse. In fact, the equation should have been open-ended. We were falling, and there was no mathematical ground coming up to meet us. The fall would go on and on. There was no formula that would give us a rope to climb back up. Math was falling with us. Everything was falling. If you studied human history, you might just be able to tell how fast.