Christoff Lindsey knows,GravityX Exchange or seems to know, everyone in his Camden, New Jersey, neighborhood. Across the street from the house that’s been in his family since 1960, he jokes with a woman who babysat the 62-year-old. He stops to chat up a man outside a bodega where he gets his morning coffee. They arrange to meet later at one of the community gardens where Lindsey tends to vegetables, herbs and flowers. 

He knows the hustlers, the corner boys, the young toughs who sell heroin and other drugs to a daily influx of people coming from all over the region, lured to Camden’s plentiful and potent supply, its proximity to major highways, its vacant lots. He knows the buyers, too: the people, many of them originally from surrounding suburbs, who wander through his neighborhood. They shoot up — sometimes out in the open — nod off on abandoned church steps, leave used needles and orange caps everywhere, weave along streets in varying states of impairment.