It's the middle of the troubles.

Violence is tearing through Northern Ireland,

IRA bombings, loyalist shootings, and soldiers marching the streets.

Even civilians find themselves caught in the crosshairs.

The gunman pointed the gun at me and says,

you have 24 hours, you get out of Ireland.

We left the house that night and we never returned.

He was stripped naked. He was beaten. He was set on fire.

My father was covered in blood.

I remember just shouting, they've missed me, but they've got my dad. They've missed me, but they got my dad.

Gunmen get away and crimes go unpunished.

Then, survivors discover there's something more sinister going on.

He is probably the most high-profile British agent that we know of to date.

A clandestine unit of the British Army is secretly running spies in the terror groups,

and it's connected to a series of unsolved murders.

If you could recruit somebody who was a terrorist, that's the cream on the cake.

To keep your cover, you need to do the business of terrorism, which is killing.

Decades later, families are searching for answers.

A lot of the answers that we need, somebody has them in the palm of their hand.

The infamous double agent steak knife is just the tip of the iceberg.

There wasn't just one agent. Most of them were agents. And the British state is still trying to cover its tracks.

Cara Hi, I think we can now show just how far the British government has gone

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