Knock-Knock

He knocked. He said there was a leak. And when they opened the door, their lives changed forever.

For nearly a decade, a predator moved through the Bronx, targeting women and young girls in their own homes. He was cunning, brazen, and maddeningly lucky. Witnesses described him so differently that police ended up with twelve sketches of one man. Every lead seemed to end with the same frustrating words: needle in a haystack.

Detective Paul Morrison of the NYPD's Bronx Special Victims Squad made...