Lenz starts demapping animals (p. 540)
He’s mastered the streets’ cockeyed grid around Enfield-Brighton-Allston. South Cambridge and East Newton and North Brookline and the hideous Spur. […] He moves nightly through urban-animal territory. […] He prefers to move north but will move east or west on the streets’ good sides.
Context
Lenz abroad after meetings, scanning before he knows what for. The narration hands him the theme's whole vocabulary in one paragraph — a mastered grid, a nightly territory, a compass preference — so that when the kills start they're already framed as something done by a navigator to the inhabitants of a charted space.