He knew other things, too. He knew that prime numbers seemed to appear unpredictably until you stopped demanding that they behave nicely. He knew that the cracks between the tiles outside the school cafeteria formed something a mathematician would call a network, and that changing where one line crossed another could turn an easy puzzle into a difficult one. Most of all, he knew that problems made him feel less powerless. A difficult problem did not care how much money his mother earned; if he could understand its rules, he had a chance.
That afternoon he was coloring maps. Two neighboring shapes were not allowed to share a color, and he had begun wondering what happened when a small design repeated again and again, extending beyond the edge of the page. He taped sheets of graph paper together and copied one patch across several rows. Sometimes the colors joined neatly at the seams, and sometimes they collided where he had expected them to fit. It bothered him in the pleasurable way a loose tooth bothered him: he kept touching the problem because he could not leave it alone.
"You still here, Professor Brooks?" called Ms. Johnson, his fourth-grade teacher, stopping at the doorway. She was carrying a stack of worksheets and a coat whose lining had begun to tear. Elijah pushed his glasses up his nose and showed her the taped pages. "Why does it work inside each square but not where the squares meet?" he asked, looking honestly troubled. Ms. Johnson put down the worksheets, pulled out a chair, and stayed with him until the custodian turned off half the corridor lights.
Ms. Johnson was not a research mathematician. She had studied elementary education, spent twelve years teaching children whose homes were often more complicated than adults realized, and understood that answering a question too quickly could close a door. "I don't know," she admitted. "But I know someone who might help you figure out what question you're really asking." She wrote an address on the back of a spelling quiz: Roxbury Community Math Center, Saturday, ten o'clock.
The center occupied two rooms above a neighborhood laundromat. Its windows faced a bus stop, and its secondhand tables had scratches left by generations of homework. Dr. Sarah Okonkwo, a Nigerian American mathematician who had once worked in university research, ran it with volunteers, donated computers, and a confidence that stubborn problems deserved patient attention. Children wandered in for tutoring, snacks, competitions, or simply a warm place where somebody would notice if they were missing.
Elijah arrived carrying his folded papers in a grocery bag. Ruth stayed beside him because she did not yet trust a place she had never seen, and Nia came because Saturday breakfast at the center included oranges. Okonkwo listened while Elijah explained his colors, his repeated tiles, and the trouble at the seams. Then she asked him a question that would change the next year of his life. "What do you mean by 'the same pattern'?"