Luther” never got any better than it was in its first go-round, thanks to sparks that flew between Idris Elba and a pre-“The Affair” Ruth Wilson. Yet if the fourth installment, presented by BBC America as one long movie, has a certain rote quality to it — especially after the title character’s break from the grind last time out — there’s still fun to be had in watching Elba occupy this role, playing a troubled detective who has the misfortune to run across a lot of bad guys prone to committing truly sadistic, gruesome crimes.

Without giving too much away, it takes another personal loss — for a character that has already suffered a lot of them — to rouse Elba’s John Luther from his idyll and semi-retirement at a seaside cottage that looks borrowed from “Broadchurch.” Pretty soon, though, quite a lot is happening, with Luther not only investigating that personal matter but being drawn into the hunt for another serial killer, and working with a young detective (“Game of Thrones’” Rose Leslie), who obviously hasn’t heard about his track record with partners.

Finally, there’s Luther’s run-in with an old-school criminal (the always-reliable Patrick Malahide), who responds by ordering up a hit against him, so that you never know when someone will randomly try to off the title character; and a self-described psychic (“Da Vinci’s Demons’” Laura Haddock) who insists she has information from the great beyond to assist Luther.

Once again, writer Neil Cross taps into deep-seated fears, linking voyeurism and technology, with a killer (John Heffernan) who observes his victims before slaying them. The body count, frankly, begins to grow a bit wearisome, but it’s broken up to a degree by the alternating threads that occupy Luther’s time. (There’s also one especially jarring moment in the early going.)

The message, ultimately, is that like a lot of hard-bitten detectives, Luther is inextricably drawn into this world, steeped in a darkness that allows him to see into the minds of these psychopaths, but that invariably exacts an inner toll. Elba wears all of that on his face while often saying very little, and even if it’s a pretty familiar conceit, he and Cross (working with director Sam Miller) have more than made it their own.

For all that, the third installment’s conclusion — which really felt like it could have been a series finale — makes this return feel a trifle superfluous, to the point where the cat-and-mouse game has lost some of its allure. It’s telling, too, that each “season” has progressively shrunk from six chapters down to two, presented here as a movie that runs slightly under two hours sans commercials — a testimonial to both the scaled-down narrative and, perhaps, how in demand the able Elba has become since we saw him last.

Then again, that’s in part because the previous chapters rather logically built on each other, making Luther’s decision to leave feel less like an arbitrary break than an inevitability. That’s not to say it’s not somewhat reassuring having DCI Luther back on the case. It’s just that after the assortment of lunatics that have passed into his orbit, and the perils he’s endured, the copper really deserves a chance to savor that ocean view.

TV Review: ‘Luther’

(Movie; BBC America, Thur. Dec. 17, 9 p.m.)

  • Production: Filmed in the U.K. by BBC Drama.
  • Crew: Executive producer, Elizabeth Kilgarriff; producer, Marcus Wilson; director, Sam Miller; writer, Cross; camera, John Conroy; production design, Paul Cross; editor, Elen Pierce Lewis; music, Paul Englishby; casting, Andy Morgan. 165 MIN.
  • Cast: Idris Elba, Rose Leslie, Laura Haddock, John Heffernan, Patrick Malahide, Dermot Crowley, Michael Smiley, Darren Boyd