Kathmandu, Feb. 17 -- Women thronged the dirty, narrow lanes, lit only by the dim yellow of light bulbs. Children darted in and out of shadows. The men came and left.

"The stench in that place was unbearable. Days would bleed into nights. Time didn't matter, nothing did," says Malika, who was 12 at the time and worked as a sex worker for more than eight months in Kolkata's red light district. "All I wanted was to leave the place, or die."

A year before, when she was 11, Malika had run away from her home in Mahankal, Sindhupalchok, to escape child marriage, a tradition that was rampant in her village. She headed to Kathmandu, thinking little of what she would do once she reached a city that was a stranger to her.

In Kathmandu, she found...