The U.S. is the world leader in solitary confinement, with more than 80,000 prisoners being held in isolation. But in recent years, more than 30 states have begun to experiment with reforms aimed at reducing the use of solitary.

On Tuesday, April 18, FRONTLINE presents Last Days of Solitary — a searing, two-hour exploration of this controversial practice from producers Dan Edge and Lauren Mucciolo.

With unprecedented access to the solitary unit at Maine State Prison, Last Days of Solitary portrays the psychological disintegration of prisoners locked in isolation, the challenge of how to deal with men considered the most dangerous and difficult in the state, and what happens when prisoners who have spent considerable time in solitary try to integrate back into society.

Filmed over three years, the documentary is a haunting portrait of life in solitary, and a unique examination of one prison’s ambitious experiment to decrease its use.

“What it boils down to is: what are our prisons for?” says Edge, who began investigating incarceration in America for 2014’s Solitary Nation and Prison State. “Are they there simply to punish? Or are they there to rehabilitate prisoners and make us safer long-term?”

The following week, on April 25, we’ll bring you The Fish on My Plate, in which bestselling author and lifelong fisherman Paul Greenberg (Four Fish; American Catch) sets out to answer the question, “What fish should I eat that’s good for me and good for the planet?”

As part of his quest to investigate the health of the ocean — and his own — Greenberg spends a year eating seafood at breakfast, lunch and dinner, a journey that’s brought to life in this 90-minute documentary produced by Neil Docherty, David Fanning and Sarah Spinks.

With people worldwide consuming more seafood than ever, Greenberg also explores questions of sustainability and overfishing, traveling to Norway, where modern fish farming was invented; Peru, to witness the world’s largest wild fishery; Alaska, where 200 million salmon can be caught each year; and Connecticut, to visit a sustainable ocean farming pioneer who is trying to transform the fishing industry.

Along the way, Greenberg comes away with surprising revelations about the fish on your plate. “A piece of fish in an American restaurant,” he says, “travels an average of 5,000 miles before you get to take a bite.”

Also this month, we’ll bring you a rebroadcast of Secret State of North Korea, our 2014 look inside one of the most tightly-controlled countries on earth.

Here’s a closer look at our April lineup:

April 4: Secret State of North Korea

With undercover footage and firsthand accounts, an inside look at life in Kim Jong-un’s North Korea. Dramatic stories of recent defectors show how some North Koreans are defying the authority of one of the world’s most oppressive regimes.

April 18: Last Days of Solitary

Airing at a special time (9 p.m. EST/8 p.m. CST), this gripping, two-hour documentary offers a window into life in Maine State Prison’s segregation unit, as officials there and across the country re-think the system. Filmed over three years, Last Days of Solitary traces the prison’s reform effort, the experiences of five inmates who have spent considerable time in solitary, and what happens when such prisoners are released back into society. With intensity, depth and clarity, the documentary shines an unblinking light on a world largely hidden from public view.

April 25: The Fish on My Plate

In this engaging documentary for any consumer who cares about his or her own health, and the health of the planet, FRONTLINE chronicles Paul Greenberg as he explores what’s happening in the world’s oceans and fish farms — and as he consumes over 700 fish meals in hopes of improving his health through a dramatic increase in his omega-3 levels.

Check your local PBS listings for air times.

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