The Tail
You and Finn tail him for a day, using the techniques in Finn's encyclopedia (chapter nine: Following Things That Might Follow You Back), and by dusk the dossier has grown alarming.
He doesn't eat. He bought a sandwich at the store — watched Mr. Otis's hands the whole time like the sandwich was a ceremony — then sat on the bench with it for an hour and gave it, untouched, to the ducks. He doesn't blink right; he blinks on a schedule, like he's remembering to. He gave the iron fence by the church a margin of six feet, crossing the street to keep it. And when a truck backfired on Elm, every kid on the block jumped — and he froze, ears-first, in a way human ears do not lead.
But the dossier has a second column, and it's the one that keeps you up. He stopped at the kickball game on the green and watched for forty minutes with his hands hooked in the fence wire, and the look on his face wasn't a scout's look; it was the look through a bakery window. He crouched by Mrs. Patel's marigolds — the regrown ones — for a quarter hour, not sniffing for anything, just looking. And at dusk, when the streetlights hummed on, he stood under one in its circle of light for a long moment, and put his hand out into the glow, and turned it over, palm-up. Like it was warm. Like it was rare.
It's at exactly that moment — the strangest, softest moment of surveillance in Brigade history — that dusk finishes falling, and his shadow stretches long across the sidewalk, and it is not the shadow of a boy.