The Arithmancy he worked on in the mornings, before the heat peaked.
He had thought it would require significant effort. It required significantly less than he'd anticipated, and he had anticipated considerably less than most people would have, because he had an engineering degree from a previous life that had included four years of applied mathematics at a level that made third year Arithmancy feel like a warm-up exercise.
The magical elements were genuinely new. He gave them genuine attention. The system of Arithmancy was a mathematical framework with magical principles woven through it that were not reducible to conventional mathematics, and glossing over those elements would have been the mistake of someone who thought the scaffolding was the building. He worked through them carefully, cross-referencing the curriculum texts with the pensieve memories of the fifth year demonstrator he'd purchased in Wiseacre's, who had the specific gift of explaining magical mathematical principles in terms that connected them to their practical applications.
By the time they left Egypt he was working at the fifth year level in Arithmancy. Not through extraordinary effort. Through the specific advantage of a framework that other thirteen-year-olds simply didn't have, and the discipline to use it properly.
He thought about the engineering degree occasionally, in the same register as all the things from before — present, real, and not quite reachable, like a room you remembered perfectly but couldn't currently enter. He had liked the work. He had been good at it. There was a specific satisfaction in a calculation that came out cleanly that was the same satisfaction regardless of whether the mathematics involved steel or magic, and he was glad to find it still available.
The evening before they left, the family ate on the roof of the rented house.
His mother had made mahshi again, with the confidence of someone who had made it once, understood what she'd done, and made it better the second time. There was bread from the bakery two streets over, and konafa from the same place, and mint tea that his father had been making every evening since the second day with the focused enthusiasm of a man who had discovered something he intended to recreate at home.
Cairo was doing its evening thing around them — the sound of the city, layered and continuous, the specific quality of a place that didn't so much quiet down in the evenings as reconfigure itself into a different kind of busy. Above it, where the city's edge met the sky, a few stars were winning against the light.
Percy was reading, because Percy was always reading and had made his peace with the fact that this was not a criticism.
The twins were engaged in what appeared to be a quiet planning discussion of considerable consequence, which they interrupted whenever anyone looked at them, which was not nearly as subtle as they believed it to be.
His father and mother were talking in the low, comfortable way they talked in the evenings, his father's hand over his mother's, the conversation of two people who had been talking to each other for long enough that silence and speech had become roughly equivalent in their ability to communicate.
Bill was on his other side, the Cairo survey text open in his lap, making notes in the margins in the particular shorthand of a professional who had developed their own notation system and had stopped worrying about whether anyone else could read it.
Ginny was leaning against his shoulder.
This had happened incrementally over the course of the trip, the way things that weren't deliberate sometimes happened — the gradual movement toward what felt safe, not sought but arrived at through accumulation. She had sat beside him at dinner on the third evening. She had walked beside him through the bazaar on the fourth. She had shown him the things she found interesting and received his genuine interest in return, and gradually, the way plants grew toward available light, she had moved closer.
He put his arm around her shoulders and didn't make a thing of it.
She didn't say anything. Neither did he. Above them, more stars were winning.
"Can we come back?" she said, after a while.
"Someday," he said.
She nodded against his shoulder, apparently satisfied, and they sat in the warm Egyptian evening while the rest of the family occupied themselves around them. He thought about what the next year was going to bring. He thought about what he'd built over this summer toward meeting it, and about what remained to be built, and about the long careful work of preparing for things you couldn't fully prepare for. He thought about Sirius, recovering in St. Mungo's with his clear grey eyes. About Harry, at the Dursleys' counting down the days. About Hermione, who had written him a twelve-page letter about the Ministry examination requirements and was probably, at this exact moment, doing something inadvisable with her summer schedule.
He thought about a city on the coast of Kerala that he remembered perfectly and couldn't return to, and about the sister he'd known there, and about the specific quality of a warm evening and the sound of a city doing its complicated living all around you.
He held the thought briefly. Let it go.
"Ron," Ginny said.
"Yeah?"
"Thank you." She paused. "For this summer. For — all of it."
He thought about what she meant, which was not only Egypt. He thought about the beginning of the summer, when she had come home from Hogwarts with the fragile careful quality of someone still reassembling themselves, and he thought about the small consistent attentions — the meals he'd made sure she ate, the conversations he hadn't pushed, the times he'd simply been present without requiring anything in return.
"You don't need to thank me for that," he said.
"I know," she said. "I'm doing it anyway."
He squeezed her shoulder once and didn't say anything else.
Above them, Cairo's sky was doing its best, and the stars that were winning were winning clearly.