We focus on the part of the internet that most people don't know about.

It's called the dark web.

Undercover in the furthest corners of the dark web,

US special agents are on a mission to locate and rescue children from abuse.

Move in now.

Police!

From the BBC World Service, World of Secrets, the darkest web follows their shocking investigations.

Listen on BBC.com or wherever you get to your BBC podcasts.

When I was a kid, I had a weird relationship with the road on which we lived.

There was always this strange sense of dread about it.

Something about that road made me feel uneasy.

It's because I was told that years earlier,

a young boy who was trying to cross the street to go and buy some milk

was run over and killed.

But later, I found out that wasn't the truth.

There'd been no road accident.

No milk.

This boy, when I did eventually see a picture of him, he looked familiar.

Light brown skin, thick, shiny hair and this enormous, contagious smile.

What did happen back then was much scarier than what I'd been told, and a lot more horrific.

Maybe the worst thing you could ever imagine.

I started searching for news articles, doing my own research, and asking questions.

...