Beneath New York City runs a second city: disused subway tunnels, active train lines, drainage channels, and the cables and girders of bridges most residents never look up to see. Director Andrew Wonder follows urban explorer Steve Duncan on a nighttime route through this infrastructure, climbing bridge cables, wading through tunnels, and crossing catwalks that were never built for sightseeing. The camera stays close to Duncan as he reads the city through its underside, tracing how subway lines, sewers, and bridge structures connect into one continuous system that most New Yorkers only ever experience as a subway platform or a skyline. There is no narrator standing outside the action explaining what things mean; the trip itself, filmed handheld in tunnels and on exposed steel, carries the film. Coverage of the expedition by the New York Times and NPR gave it wider attention after release. It runs short, more a single expedition captured start to finish than a survey of urban exploration as a movement, and it treats Duncan's route as the whole story.