SPOILER ALERT: Do not read if you have not yet watched the season finale of “Mare of Easttown.”

“Mare of Easttown” has, from its first moments, been something special even in a very crowded lane. The prestige-actress-led murder mystery on HBO has, in recent years, seen outings that have achieved varying degrees of creative success, among them “Big Little Lies,” “Sharp Objects,” and “The Undoing.” One element that differentiated “Mare,” finally, was that it really stuck the landing, delivering an ending both of narrative wholeness and of real emotional power. But what had set this series apart from the beginning was its deep and abiding sense of setting, in small ways and in large. In its final moments, “Mare of Easttown” beautifully communicated its series-long central idea: Living in a place that insists one give up, one must still try to find a way through.

To deal with the specifics of that ending before moving on to grander thematic concerns: The notion that John Ross had been the killer of his former lover Erin was an elegant reversal of suspicions that had been placed upon his brother Billy. This was all so neat that viewers could be forgiven for not quite realizing the mystery portion of the series seemed completely wrapped up with some half an hour of the finale still left to air; plotlines, like Guy Pearce’s gentleman caller leaving town, were being wrapped up with a lovely melancholy. Then, suddenly, came the second reveal — that John had been covering for his son Ryan, the real killer. This was elegantly dealt with, a realization that dawned for Mare on a standard work call, and Winslet did some of her best acting of the series processing it all for a long moment. Her responsibility to her perception of justice outweighed her responsibility to the Ross family. What this added up to, though, was a double tragedy of lost youth. Not merely was Erin McMenamin dead, but her killer’s future was over.

“Mare of Easttown” thus gave us a genuinely surprising conclusion that satisfied the viewer desire for memorable, twisty shock. It also completed a statement it had been making from its first episode. Ryan Ross was drawn into the morass of family drama and sorrow at a tender age; at a time when he might otherwise have been looking ahead, he found himself obsessively working over hurts in his family history. We had seen Ryan’s propensity to turn to rage before, when he violently defended his sister in what we were meant to understand was displaced rage over his father’s infidelity. While Ryan’s anger was extreme, it was not unique: In his story, we see a parallel to Mare’s late son Kevin, a young man lost in rage, confusion, and isolation. Mare has recalled his brutalizing her for money for drugs, as well as his death by suicide in her attic; she misses him desperately, to the point that she cannot enter the room in her house where he died.

Had Ryan not actually killed Erin — had he simply been an angry young man who was willing to, say, beat her — we see in Kevin’s story where things might have led. The deaths on “Mare of Easttown” catch our attention, but the show’s longer-lasting heartbreak comes from the lives, from those who survive. It was easy, at times, to mock elements of the show’s fixation on its setting: The chewiness of the accent, the bouquet of hoagies one foreign-born movie star presented another, the Rolling Rocks. But “Mare” had a big and painful conception of Easttown: It was a place, like so many in America, that feels hard to escape. Opioids quietly thrum under so many interactions (given the baleful story of Kevin and his girlfriend, who begins using again over the course of the series, they’re a subject very much on the show’s mind). Accreted history has blotted out possibility. There were real, mutually supportive relationships all through Easttown — life there isn’t unlivable — but those relationships tended to be based on supporting one another through pain that seems endless. Think of why John and Erin first came together: John tells us that they were both going through a hard time. Or think of Winslet — her whole heavy-footed performance a study in endurance, supporting Lori (the great Julianne Nicholson) through her own pain. Mare seems to discover within this frighteningly raw moment a strength that surprises even herself.

It’s instructive to compare the ending of “Mare of Easttown” to that of “The Undoing.” That latter episode was widely pilloried when it aired; to this viewer, it wasn’t horribly out-of-step with what had come before, a fun, underbaked show that gave us a few thrills and some nice-looking coats. But the big reveal of “The Undoing,” that Hugh Grant’s character could be pushed to the point of madness, had effectively nothing to do with the Manhattan milieu the show had taken great pains to evoke visually. “The Undoing” took place in a specific and carefully drawn world, about which, finally, the show had little more to say than that sometimes, people like Nicole Kidman’s character can be blind to the obvious. Why had we been on this ride in the first place?

“Mare” made its case for itself with, given the heaviness of the themes at play, a startling deftness of touch. This series is suffused with a deep idea of where it’s set, who its characters are, what it is they want and what they’ve accepted they’ll never get. And each of the cast’s portraits in miniature worked together to lend a sense of a town trapped in amber — the series began with squabbling among the much-remembered champion Lady Hawks team that lent the sense of a town where the same conversation never ends. The endless back-and-forth between Winslet’s and Jean Smart’s characters was a similarly well-worn dynamic; what we learn, finally, about the Ross family’s working together to try to salvage something irreparably broken suggests that all over town, families have their own codes, all united to work against change.

Some change, like the incursion of drugs and desperation into a town where the Lady Hawks once soared, is bad but must be borne. Other sorts can be good, or at least hopeful — but need to be fought for, every inch of progress gritted out. Mare, we’ve learned over the course of this series, is a brilliant cop and brilliant, too, at sabotaging herself. What she lacks is imagination, the ability to see herself into another place. The beauty of the final episode lies in where it pushes her, beyond the limits even of what a person who prides herself on her stoicism can bear. Amid the broken pieces of herself, something shifts.

Over the course of a remarkable run of episodes, Mare has done what she’s good at (crime-solving) and been forced to do what she’s not. She’s been made to look closely at her life and to contemplate what it might really mean to get over pain, to bring herself a bit of the relief she tries to bring others. How absolutely fitting that the series ends with Mare finally going up to the attic, to allow herself to really feel her feelings about her son’s death and, possibly, to begin bringing herself somewhere new — if not outside Easttown, then at least a new frame of mind. A show all about being stuck in place gives its central figure, and us, a final gift: Allowing her to begin a process that all of Easttown has seemed united in beating back, and to use what she’s found in herself to begin moving forward.