A Wall Street trader quits his job to roam the toughest streets of the Bronx.

Four years ago, a Wall Street trader named Chris Arnade wandered into Hunts Point, a Bronx neighborhood nestled in the poorest Congressional district in the nation and often referred to as New York City's red light district. He didn't know why he was there, but he had his camera, and he started snapping photographs.

Then he came back. Again and again. Soon he started writing about what he saw there, posting both images and text on Facebook, Flickr, and Tumblr, and capturing the cycle of abuse, drugs, and sex that kept people chained to the neighborhood.

His work -- about the weapons carried by prostitutes; about abuse from pimps called Payroll, Mosquito, and Escrow; about oral sex, the currency of the desperate -- shocked many of his Wall Street colleagues, and occasionally, his three teenage daughters.

In early 2012, the New York Times featured his work. But in the past several months, much has changed: He quit his job with Citibank and now spends about five days a week with the Hunts Point crew, often working with journalist Cassie Rodenberg. His subjects have ceased to be merely subjects, he says, and they've pulled him down a twisty, intimate path from which he believes he cannot escape.