WHAT IT’S ABOUT Det. Chief Inspector John Luther (Idris Elba) is trying to put the past behind him — especially his complicated past with Alice Morgan (Ruth Wilson, not appearing here). He’s living in a seaside cottage perched on the cliffs of Dover, when a knock comes at the door. A pair of cops from London, including DS Emma Jones (Rose Leslie of “Game of Thrones”), want to know what he can tell them about Morgan. Not much, says Luther. And then they break the news. Before long, John must leave his seaside idyll for the city: A serial killer is on the loose. (Again.)

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This two-hour movie, billed as a “special event,” could be a setup for a big-screen “Luther,” something Elba wants to do.

MY SAY Gone a couple of years now, “Luther” — like any cop show — was always an acquired taste, but one I never particularly acquired. Too gruesome. Too many psychosexual/sadomasochistic serial killers. Too much blood, too. But “Luther’s” appeal wasn’t necessarily the content as much as the star — who commands the screen, and fixes both the viewer’s gaze and attention. That’s called “charisma,” even though Elba as DCI John Luther added (and adds) more layers: Virility and power saddled to an inexpressible melancholy. Yeah, TV cops going back to Columbo have been cauldrons of Conflicted Emotion, but his Luther moved well past that archetype — or cliché — to create someone more harrowing, dangerous and interesting.

Clearly Elba — a big star now — relished this reunion. Luther still walks down those London streets like he owns them. He’s still convulsively and compulsively violent. Scores need to be settled and mostly are.

But some of those people who completed him in some psychic sense are not along for this ride: Morgan, who was a manifestation of his darker angels, is gone, and so is DS Justin Ripley (Warren Brown), who represented the better ones. Ripley died last season, the fate of Morgan will be revealed Thursday. But even with Emma Jones by his side, John Luther seems more alone — or isolated — than ever.

BOTTOM LINE The story feels recycled, but Idris Elba’s Luther certainly doesn’t. He continues to fully inhabit this groundbreaking — and star-making — role.