This is the Guardian.

This week we're revisiting some of our favourite episodes of the year so far.

We begin with a today-and-focus special investigation,

the division New Orleans.

One episode a day for the next four days.

A US Southern Bureau Chief Oliver Lockham spent six months following what happened

when a progressive black district attorney called Jason Williams was elected in Louisiana,

the heart of the deep south.

Jason had promised sweeping reforms across the city of New Orleans,

but he had no idea just how hard that would be.

Do stay with us to the final episode for an update on what's happened since the series first aired

back in May.

And just a heads up, before we start, this series features strong language and depicts scenes of violence.

One day this spring under blue skies on a searing hot New Orleans day,

a go-for-a-walk with Keith Plessy.

Well, we're here in New Orleans one day before Madagra, it's called Lundegra.

The Monday before Fat Tuesday.

We're walking through by water.

It's the neighborhood where I live and something that could only happen in New Orleans happens.

All of a sudden, as we walk, this huge parade comes out of nowhere and kind of envelops us.

Everyone is strolling along, drinking beer, wearing beautiful, incredibly elaborate costumes.

But the parade isn't why I'm out here with Keith.

...