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This episode contains a sectarian slur and depictions of alcoholism. Please be advised.

1972, Derry, Northern Ireland.

Willie Carlin walks through the city centre, enjoying the summer sunshine.

He's a lean, wiry Catholic with strawberry blonde hair and a sergeant in the British army. Since enlisting in the army

seven years ago, he's been stationed in Germany. But now, ahead of a transfer to Dorset, England,

he's back in his home city, visiting family with his wife, Mary. But the dairy they knew is gone.

Since they left, the long-simmering tensions

between Northern Ireland's Protestant and Catholic communities

have erupted into armed conflict.

The Protestants want the province to stay in the United Kingdom.

The Catholics wanted to join with Ireland.

So now, the British Army patrols the streets.

It's supposed to be here to stop the violence.

But then, the government introduced internment,

imprisonment without trial,

to crack down on paramilitary groups like the IRA, which opposes British rule.

Protests followed.

Then, a few months ago, less than half a mile from where Carlin's now walking,

British troops opened fire on a march against internment.

Fourteen unarmed protesters were killed.

It's being called the bloody Sunday massacre.

...