It's such a pleasure to watch Idris Elba periodically return to television as British cop John Luther that it can be easy to ignore for a moment what a mess "Luther" the show is around him.

The mystery series, which returns to BBC America for a four-night run beginning tonight at 10, is a fantastic showcase for "The Wire" alum Elba. The brilliant, damaged homicide detective who has far too much in common with the killers he chases is a very familiar archetype, but one the right actor with the right material can still work magic with. As FBI profiler Will Graham, one of the originators of the trope, Hugh Dancy's doing great work on NBC's "Hannibal," and Elba is riveting as he does his bow-legged strut through the streets of London, making amazing intuitive leaps and engaging in dangerous gambits to find and stop the bad guys. Luther's not an original character, but he's a memorable one, and the short commitment of a British TV season allows Elba to keep taking breaks from his busy movie career to do the show.

But oh, those bad guys! We're three seasons in, and "Luther" creator Neil Cross continues to fetishize his killers' crimes in the same way they in turn fetishize their victims. The British accents create the illusion of classiness, but "Luther" falls prey to the same Awesome Serial Killers Are Awesome ethos that infects "Criminal Minds," "The Following" and most other shows in the genre that aren't "Hannibal." ("Hannibal" avoids these pitfalls both by being so imaginative with its killers' methods that it feels more like science fiction than a police procedural, and by having a sense of humor most of these other shows lack.) "Luther" relishes images of its killers popping out from under beds or from inside closet doors as helpless victims squeal in terror (and virtually never dial 999, even when there's ample opportunity to do so), and the chunks of each episode dealing with the killers rather than Luther's hunt for them are unpleasant in the extreme.

Cross could be making an argument that crimes this nasty require a brilliant rule-breaking cop like Luther to solve, but the writing gets very muddled whenever we're asked to question Luther's ethics. The new season has Luther's partner Justin Ripley (Warren Brown) approached by a pair of internal affairs cops who believe Luther has gone too far over the line, but they're so shady that we're never meant to take their concerns seriously, even if we sympathize with Ripley's doubts. And the brief season's second half has Luther going up against a vigilante who's killing criminals who escaped justice on technicalities.

The killer comes face to face with Luther at one point and asks if he's ever been tempted to take the law into his own hands in this way, and Luther insists he doesn't have the right to do that... even though the very first episode of "Luther" opens with Luther letting a pedophile fall to his death when he could have easily saved him, and has featured other situations where Luther at a minimum puts bad guys in positions to be killed by others.

Either the investigation into Luther or the vigilante's campaign could have asked interesting questions about what our hero is really doing, and made the audience question its sympathies for him. Instead, like "Dexter" (which is limping through its farewell season), the show doesn't want anything but adoration for its charismatic leading man.

And Elba's fabulous, particularly in the all-too-brief moments in the series when Luther gets to interact with Ruth Wilson's clever sociopath Alice Morgan. (Even though we're always meant to take Alice seriously, Wilson's presence adds a light touch the rest of the show desperately lacks.)

But he and Wilson deserve a better, and smarter, show than the one they've been a part of the last few years. ("Luther" always suffers from wobbly plotting, and the season's closing minutes require an entire suspension bridge to hold up the audience's disbelief.)

Having to only do a handful of episodes a year keeps Elba coming back. Having to watch only a handful of episodes does the same for me; if "Luther" were substantially longer, I wouldn't have the patience for it. Four hours is brief enough that the joy of seeing Elba back on TV outweighs the silliness of "Luther" as a whole.

Alan Sepinwall may be reached at sepinwall@hitfix.com

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NOTE: Blog spoiler rules are the same as always: if it hasn't aired yet in the United States, we treat it as a spoiler here. Even though I'm sure many of you either watched the season in the UK or via extra-legal means, we're not going to discuss plot details until the end of the week; I'll put up a post on Friday night so we can talk about it all once everyone's on the same page. Got it?