Luther's comeback season tottered its way to an explosive if slightly bleary ending. Our harrumphing hero (Idris Elba) was dragged away in handcuffs – and he got off lightly compared to Alice Morgan (Ruth Wilson), who, not for the first time, the series took great delight in killing off. Presumably she is dead for good on this occasion. 

There was also a resolution to the killer surgeon storyline, albeit one that appeared to borrow heavily from a 20 year-old episode of I'm Alan Partridge. 

The Luther-George Cornelius (Patrick Malahide) feud was wrapped up with a bow, too, thanks to an impassioned plea from the former that they set their differences aside. 

Not that this prevented crime boss Cornelius from betraying Luther and stitching him up with a picture that appeared to show the noble detective chief inspector killing in cold blood. 

But did any of it make any sense? The short answer, many viewers might conclude, is not really. For the long answer read on as we delve into the episode's talking points. 

Where does DCI Luther go from here? 

Luther has been implicated in the murder of his Met pal Benny Silver and arrested by his already suspicious boss DSU Martin Schenk (Dermot Crowley). 

The smoking gun was a picture of a smoking gun taken by George Cornelius after he (George) had shot dead assassin Palmer (Anthony Howell). 

But the snap suggested it was Luther who had pulled the trigger – and thus also made him a person of interest in the death of Silver. The latter's body was helpfully stashed in Palmer's van. Convoluted? Strap in – we're just getting started. 

Is Alice really dead? Or just Luther 'dead'

Alice has been written out of Luther previously only to make a surprise comeback. She would seem to have thrown her last killer glance however having essentially flung herself to her death after chasing Luther around the moody building site. 

Our favourite sociopath had turned on her romantic interest after he lied and told her that he had killed George when in fact he and the kingpin had hugged and made-up. 

Every bit as paranoid as the next murderous psychopath, this had flicked a switch in Alice. She resolved to take out George herself and popped up at his kitchen window with a machine gun. 

Unfortunately for her, Schenk had sent the equivalent of a Swat team around and so Alice's thirst for vengeance was left un-sated. Never mind – she could still get her own back against Luther. 

Was Halliday's death the biggest shock?

Luther writer Neil Cross likes to pile twist upon twist so that the results are more tangled than headphones left in the wash. And so it went here. No sooner had Luther and DS Halliday (Wunmi Mosaku) foiled killer Jeremy (see below) than Alice popped up and shot Luther's new side-kick. In hindsight, this has been bubbling up for some time as Alice had been upfront about her jealousy of Halliday. 

Again, it didn't make a huge degree of sense – Alice was not for the first time behaving like a wandering plot device rather than a real person – but it was a jolt from the blue that made you sit upright. 

Was the killer storyline an afterthought? 

When not dashing around London trying to find his kidnapped pals, Luther also had a deranged murderer to stop. Jeremy (Enzo Cilenti) went back to the scene of an earlier crime, the house belonging to the terrified teacher from episode one. 

There, he embarked on the crazed killer equivalent of a Deliveroo binge – all in service of a game he called Happy Families. 

A plumber, a call-girl and several other victims were summoned to the address and subjected to top level recreational slashing by Jeremy – who then adorned the corpses with plastic facsimiles of his face and sat them around the telly. 

This was presumably intended to be deeply creepy but in fact carried echoes of the Alan Partridge episode in which an uber-fan lures Alan back to his house and reappears wearing a Partridge mask. Rather than chilling, it staggered towards unintentional comedy.

Jeremy's just desserts were scary though

Having worked out that Jeremy would go back to an earlier crime scene, Halliday went downstairs to investigate a ringing doorbell. In the gloom, Jeremy – wearing a Jeremy mask because why the heck not? – materialised. 

He was looking forward to cutting her to ribbons when Luther charged in and bashed the mad man about the face. A bit predictable but at least it was a clean ending that didn't cause further confusion. 

Was Hermione Norris short-changed by the series?

The Cold Feet star was great as Jeremy's enabling wife Vivien. She radiated crazed arrogance even when caught by the police and played a manipulative game until the end. 

Yet she was ultimately betrayed as Luther and Halliday shared with her the contents of Jeremy's gruesome scrapbook. It was written in a secret script which Jeremy didn't want her to understand but that he nonetheless intended for broadcast to the rest of the world. 

The idea of a blindly loyal accomplice who realises too late that her husband isn't just a monster but also a show-off was fascinating. So it was a shame Vivien was quickly forgotten about as Cross sent Luther blundering across London with Alice on his tail. 

Why did George Cornelius mend his ways with Luther so quickly? 

Contract killer Palmer (Anthony Howell) had shot Benny and left Alice and Mark to freeze to death in a warehouse. But when Luther tracked down George by having Halliday reluctantly access details of one of his goons, the ruthless gangland figure was talked out of his revenge mission surprisingly easily. 

Luther put it to Cornelius that the situation had spiralled out of control and they were better off patching up their differences and going their separate ways ("all this eye for an eye bull---t… it's all just a game George"). He even handed Cornelius his gun and invited the arch-criminal to shoot him in the head, if he thought it would do any good.

It wasn't the first occasion that Luther had made this argument (albeit without the "shoot in me in the face" bit). But for no good reason other than that the series was about to conclude, this time Cornelius agreed. So Palmer was called off – which didn't much please the assassin and he resolved to finish the job anyway. 

He was prevented from doing so by the tag team of Cornelius and Luther, who turned up at the warehouse where Alice and Mark were turning into human icicles. It resulted in a memorable stand-off while suggesting that Alice isn't the only character whose behaviour makes absolutely no sense. Having gone to such effort to eliminate Luther, would Cornelius really shrug and allow bygones be bygones? 

What does the future hold for the series? 

With Luther seemingly set to be locked away and Alice, the show's most interesting character, dead, this would be the perfect moment for Neil Cross to sign off for good and leave us wondering. However, Elba has intimated that a Luther movie is a distinct possibility. 

That's excellent news for fans – but what contortions will Cross have to pull to spring the eponymous copper out of jail and resurrect Alice yet again.