It was a warm May morning and Marc was sleeping when he heard the door to the roof terrace open. At first he did not react, just shifted the sheets a few centimeters in response to the alert stimulus. Then, after a few moments, he heard footsteps, but not moving closer, instead seeming to walk back and forth, and at times in circles. He got up and threw open the hut door. At the far side of the terrace, through the intervening formula-covered papers that hung from the lines, there to meet the weakly figure of Marc in boxer shorts, was a man. They looked at one another in silence. The man was tall, very tall, bearded, and with eyes set far apart like those of a fish; he thrust his hands into the pockets of his thick tweed jacket and advanced toward the hut, ducking under the wires as he came. Hello, said Marc. The man did not reply, merely raising a hand in a heavy sort of gesture before changing tack slightly so that he ended up not at the hut but at the edge of the roof. How alike everything looks from up here, he said, as though addressing the air. Hello, Marc said again, is there something you want? Marc saw that the man was much taller even than he had at first appeared, an impression intensified when he took a plastic chair Marc had salvaged from the scrapyard of a chalet and sat down, looking like the oldest child in school, having to squeeze into it. He lit a cigarette—offering one to Marc first, who declined—and then sat staring at the weathered sides of the hut. Marc went inside, found something to wear, and took a drink from a carton of milk before going back out, hastened by the man’s voice, Know what, young man? Marc, holding the carton and leaning against the door, said, No, what? Well, I remember a morning in my home in Paris, I’m talking 1961 or thereabouts, and I was in bed, half sitting up, leaning back against the wall, I know I also had the radio on though I couldn’t tell you what program, and I was staring at the opposite wall, at a plank of wood I’d put up, bit of a shoddy job, I was using it as a bulletin board for photos I liked, press cuttings, stubs from the cinema and concerts, food offers from all kinds of different brands, this kind of thing, I was poor in those days but didn’t concern myself with thoughts of the future, we expats lived pretty well in Paris then because we could pass ourselves off as students, and Parisians were always kind to students, but anyway, what I was saying: that morning I was gazing at the wall, distractedly, thinking about goodness knows what, a woman maybe, maybe nothing at all, and then out of that jumble of photos and cuttings my eye alighted on a line, invisible until then, which ran the length of this collage, meandering from top to bottom, passing through certain photos, words, and snippets, so that if you followed it you were presented with a composition that had, until then, been entirely invisible. And it was this supreme image that turned out to link my two masterworks, Hopscotch A and Hopscotch B, or just Hopscotch, and my Open Ball Theory. Hopscotch B, Marc immediately said, Open Ball Theory, what’s that? Well, the man said, during the writing of a book called Hopscotch I came up with a parallel theory which gave a mathematical account of each of the book’s fragments, and later called it Open Ball Theory, or Hopscotch B. That’s right, young man, working on the basis that every person comprises not just their body but also the space immediately surrounding their body, a sphere susceptible to all kinds of empathic flows, whether sympathetic or antipathetic, just like the coming and going of breath, like the intrusion of other people’s breathing, the sounds of people around you, smells and primary intuitions, et cetera, it means we can define the human species as a whole made of open balls, at times intersecting, at other times repelling one another. But Hopscotch B, that I keep to myself: that one’s not for teaching. Marc thought for a moment, and the man got up and said, pointing his cigarette at the hut, Take a proper look, young man, you’ve got a great deal of material right there, a prodigious amount, really. Marc, excited now, took another drink from the milk carton and said, Hey, sir, do you know anything about Fermionic Solitude? And the man, calmly, also unhesitatingly, said, Don’t wind me up, young man, at this particular moment winding up is not what I need. And with that he left, ducking the wires as he went. He raised the collar of his jacket and was gone. Marc stood for a long time watching the rear portions of the cars as they advanced down the wide one-way street to the waterfront shipyard. They can’t, nor will they be able to, come back along it, he thought, and he also thought about the World Cup we’ve never won, about the fact that the score to Battleship Potemkin, studied correctly, is a version of Jimi Hendrix’s “Purple Haze.” He was disappointed not to have shown the man the Philips Agricultural Guide: 1961, which has the instructions for how to build huts from used tin.