The fire started in the southwest corner of the canyon and spread northeast, claiming one diagonal strip each hour until the entire slope was alight. Then the marine layer rolled in — a wall of cold fog that smothered the edges of the burn. The perimeter went dark first: every cell on the border cooled below ignition. But the interior, insulated by its own heat, kept burning. Only the four cells in the center of the grid still glowed when the helicopters arrived at dawn. By noon, even those were out.