An Old Murder Is 'Unforgotten' In This Crime Drama's 4th And Finest Season

TERRY GROSS, HOST:

This is FRESH AIR. The British crime drama, "Unforgotten," follows a police unit that solves long ago murders. Its fourth season premieres on PBS's "Masterpiece" on Sunday. Our critic-at-large John Powers has watched the entire season and says it gets to you in ways you wouldn't expect.

JOHN POWERS, BYLINE: If you regularly watch police shows, you know that very few of them make you feel anything. For every "Mare Of Easttown," there are 20 fast-paced crime dramas, from "CSI" to "Line Of Duty," that pass off sensation as emotion. One show that is positively bursting with feeling is "Unforgotten," a nifty British series whose fourth and final season airs on PBS's "Masterpiece." Twistily (ph) plotted and suffused with sadness, this new season builds to a gaspingly emotional climax that left British viewers needing hankies the size of parachutes.

Nicola Walker stars as Detective Chief Inspector Cassie Stuart, who, along with her partner, Sunny Khan - that's the excellent Sanjeev Bhaskar - heads a unit that handles cold cases. Season 4 begins with a headless corpse being found inside a freezer in a junkyard. The victim had been killed 30 years earlier. Cassie and Sunny soon link the killing to four people, two men and two women, who were police cadets at the time of the murder. It's almost certain that one of this quartet is the killer. But which one? The likeliest culprit is Ram Sidhu, played by Phaldut Sharma, a cocky Sikh police detective known for pushing the boundaries. But it could also be bottled-up Liz Baildon - that's Susan Lynch - a chief constable who's on the verge of being promoted into the top ranks of the police. Then again, it could equally be one of the two who've left the force, therapist Fiona Grayson, played by Liz White, who has a past she finds shameful, and the squishly amiable Dean Barton - that's Andy Nyman - who runs a charity for kids.

Now, like any good mystery, "Unforgotten" is deft at strewing clues and reversals that keep you guessing. But lots of shows do that. What makes this series appealing is less the clever plotting than the deeply felt bond between Cassie and Sunny. Their blend of warmth and restraint makes them one of the most comforting duos on TV. Here, early on, Sunny brings her up to date on the case, starting off by asking if Cassie remembers when England's Marathon candy bar began being called Snickers.

(SOUNDBITE OF TV SHOW, "UNFORGOTTEN")

SANJEEV BHASKAR: (As Sunny) A fiver if you know when Marathons changed to Snickers.

NICOLA WALKER: (As Cassie) 2000.

BHASKAR: (As Sunny) Way out - 1990.

WALKER: (As Cassie) Oh, wow. Where did my life go?

BHASKAR: (As Sunny) Yeah, the victim had a Marathon wrapper in his pocket. We're checking it for DNA.

WALKER: (As Cassie) And Jake said you think he'd been kept in a freezer.

BHASKAR: (As Sunny) Pretty sure now. The lab's confirmed traces of blood in a freezer found near the body.

WALKER: (As Cassie) What, and you're thinking he'd been in there since the '90s?

BHASKAR: (As Sunny) Don't know.

WALKER: (As Cassie) Oh, weird. Why would someone keep a body for 30 years?

POWERS: Walker is one of those down-to-earth actresses that ordinary people instinctively connect to, and her Cassie is the best-case scenario of a good cop. Caring, honorable and capable of great intuitive insight, she spent years investigating cold cases with a passionate commitment that, as this new season makes clear, has left her constantly angry at the police force, her family and herself. Cassie is calmed by the devoted Sunny, whose certainly saturnine features belie the fact that he is the best-case scenario of a sidekick. Always steady, he's skeptical when Cassie tries to leap to conclusions.

From the beginning, "Unforgotten" has always cast an unusually compassionate eye on its main murder suspects. It makes a point of showing the often exemplary lives they've built in the decades since the crime they're caught up in. This season, each of the main suspects has also been warped by growing up in a difficult family. And the show takes time to show sympathy for each, to give them all a destiny not wholly defined by a long-ago murder.

This is even true of the season's best and most daring character, Ram Sidhu. Having grown up a target of racial hostility, he's internalized an angry sense of grievance that puts him on the attack with everyone except his brother and wife. He knows how to work people, mocking Sunny for being an Asian Uncle Tom or threatening to accuse superiors of racism when they try to rein him in. Wounded and slippery, Ram has a scorching complexity that is all too human.

And it's this sense of complexity that gives "Unforgotten" more of an emotional wallop than your ordinary cop show. As this new season builds toward its conclusion, you find yourself hoping that none of the suspects turns out to be the killer and that Cassie will overcome her rage and go back to working happily with Sunny. You root for things to work out for the best even as you dread they won't.

GROSS: John Powers reviewed the fourth season of "Unforgotten," which begins on PBS' Masterpiece this Sunday and will be streaming on PBS Passport and the Masterpiece Prime Video channel.

Tomorrow, we'll talk about a case that journalist Emily Bazelon says illustrates the inequality and waste of mass incarceration. Bazelon writes about the criminal justice system. Many incarcerated people ask her to help prove their innocence. She decided to try to help one of them and got her sister Lara involved. Lara runs a criminal justice clinic at the University of San Francisco School of Law. We'll hear from Emily Bazelon and the man she helped get exonerated, Yutico Briley. I hope you'll join us.

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GROSS: FRESH AIR's executive producer is Danny Miller. Our technical director and engineer is Audrey Bentham. Our interviews and reviews are produced and edited by Amy Salit, Phyllis Myers, Sam Briger, Lauren Krenzel, Heidi Saman, Therese Madden, Ann Marie Baldonado, Thea Chaloner, Seth Kelley and Kayla Lattimore. Our associate producer of digital media is Molly Seavy-Nesper. Roberta Shorrock directs the show. My thanks to Dave Davies for hosting while I took a vacation. I'm Terry Gross.

(SOUNDBITE OF SONG, "BACKHAND")

UNIDENTIFIED SINGER: (Singing) Send down to New Orleans, backhand jive and me. Have you ever been down to New Orleans? Backhand jive and me (ph)... Transcript provided by NPR, Copyright NPR.