During four seasons on ITV, the British police drama “Unforgotten” has slowly and quietly built an audience and a reputation, an appropriate method for a show in which the main characters rarely raise their voices and are immediately ashamed of themselves when they do. (The show’s six-episode fourth season begins on Sunday on PBS’s “Masterpiece.”)
That’s not to say that the two cops who lead a London cold-case squad, Cassie Stuart and Sunny Khan — beautifully and harmoniously played by Nicola Walker and Sanjeev Bhaskar — are pushovers. Cassie is anxious and awkward but also dogged and more than a little self-righteous. Sunny is a peacemaker and a loyal deputy, but he’s also a natural-born skeptic with a biting sense of humor.
What they have in common is decency, a quality that “Unforgotten,” to a greater degree than any other show I can think of, takes as its central value. As the squad works to identify the bodies of long-dead victims and figure out how they died, the brutal messiness of the stories the team uncovers is balanced, and in some sense redeemed, by their compassion and meticulousness. (Lending the proceedings an extra touch of formality is the British term for cold cases: historical crimes.)
“Unforgotten” is also familiar: at once a comfortably formulaic British mystery and a somber, elegiac melodrama, though a particularly well-made version of each. Season 4 begins with the ritual discovery of the corpse — in this case a headless, handless young man found in a scrap yard. At the same time, in short, cryptic scenes, we’re shown the people whose lives are about to be thrown into chaos by the surfacing of the 30-year-old crime: a woman biking across Cambridge to visit her domineering mother, a middle-aged man checking out the teenage girls in Southall as he brings his mum a Mother’s Day present, a couple in the Peak District mildly disagreeing over money.
The gradual revelation of who these people are and of the connections among them is one of the show’s pleasures. There is also the slow but sure progress of the investigation, in which the slightness of the clues (the serial number of a freezer, an outdated candy wrapper, a football club tattoo) and the constant frustrations (witnesses deceased, homes torn down) make the eventual deductions that much more satisfying.
Along with these typical elements of the crime drama, the show’s creator and writer, Chris Lang, and its director, Andy Wilson, use the cold-case framework to add a distinctive and, when the show is at its best, powerful element of domestic drama. Cassie and Sunny’s job is to take people back to what was most likely a terrible time in their lives, and to tear down the facades and false narratives they’ve built up over years.
To do that, the detectives need to take the journey as well, at some cost to their own peace of mind. There’s always a family being tested or torn apart; the only one that can be counted on to hang together is the one in the squad room. (The show’s portrayal of its police officers is unabashedly positive; if that doesn’t sit well, you may take some solace that the suspects in the new season turn out to be cops, too.)
Season 4 begins with the team unsettled — Cassie, rattled by the grim revelations of previous cases, has been on leave for more than a year and wants to quit the force. She’s just short of the 30 years she needs for her pension, however, and that requires her to come back for at least one more case. That premise provides good occasions for Lang and Wilson to show off the greatest strength of the series: the pitch-perfect performances of Walker and Bhaskar. It’s pure pleasure watching Cassie confront a police functionary with exquisite passive-aggressiveness and then meet Sunny for a gripe session during which, distractedly but inevitably, she begins to think through the new case. “Still got it,” Sunny says as she hurries away.
The relaxed and intimate teamwork of Walker and Bhaskar is reason enough to watch “Unforgotten,” and in the story around them Lang has generally avoided both the overt sentimentality and the sensationalism that bring down most shows of this type. He has a good ear for dialogue and a good sense for plot, and has kept a delicate balance between mournfulness and the excitement of investigation.
Until, that is, the end of the new season, when he throws in a twist — don’t Google the British reviews if you don’t want to know — that’s out of step with the show, and torpedoes the final episode. Given the ethos of “Unforgotten,” worst of all is that the episode trivializes the solution to the mystery and distracts us from the humanity of the victim, things Cassie and Sunny would never do. A fifth season has been ordered, and with luck this was a one-hour glitch.
