WARNING! This article contains spoilers of the highest order.

With the photos of Jo Davidson, John Corbett, Roz Huntley, Danny Waldron, Lindsay Denton and Tony Gates packed up into a box, there was a sense of finality at the end of Line Duty’s gripping conclusion on Sunday night.

Having finally unmasked DSU Ian Buckells as “the fourth man” – otherwise known as “H” – AC-12’s work was seemingly done, raising questions about whether we’d seen Superintendent Ted Hastings and his team solve their last case. 

After all, it wasn’t just the “H” mystery that was wrapped up neatly – so, too, were many other long-standing questions, like those that related to Hastings’ involvement in Corbett’s death and DI Steve Arnott’s addiction to prescription medication. 

But while things might have felt pretty final, closer inspection of the episode suggests there’s a lot more to the Lawrence Christopher case yet to be discovered, which could set the show up for another outing.

There’s no official word yet from either the BBC or the show’s creator Jed Mercurio about a seventh series, but given the gargantuan ratings Line Of Duty has amassed this year, we reckon the broadcaster will be scrambling to get him to write at least one more. 

Which is just as well, as there are still some loose ends that the finale didn’t tie up…

1. Will Hastings face any repercussions?

While Hastings said he was appealing his forced retirement after closing the case, the pre-credits sequence informed us that plans to slimline anti-corruption were ploughing ahead, with DCS Patricia Carmichael still in charge of AC-12. 

We can probably assume from this that Hastings did not win his appeal (at least not immediately, anyway), but we don’t know whether this might be because Carmichael also informed her superiors about Hastings’ confession regarding the events leading to Corbett’s death. 

If she did, Hastings could be facing a legal investigation, but we have no idea what will become of him. 

2. What’s Carmichael’s deal?

Just because Carmichael wasn’t “the fourth man”, doesn’t mean we haven’t still got suspicions about her – we’re convinced she has some connection to Buckells that we don’t know about.

Not only was she very keen to ensure charges against him were dropped in the previous episode, she looked positively shifty when he arrived at AC-12 HQ for questioning. 

But perhaps most significant was the panic on her face when Arnott suggested launching an investigation into whether other members of Marcus Thurwell’s team might have been involved in the cover-up of the Lawrence Christopher case, given many of them are still serving officers. She then informed him that such cases “aren’t a priority”. 

Like Chief Constable Philip Osborne, she refuses to entertain the idea there is a problem of institutionalised corruption in the force, despite being in charge of, y’know, an actual anti-corruption unit. 

Perhaps that’s because she’s concerned that a wider look at police corruption might expose her own misdoings?

As Hastings pointed out to her, Buckells could not have risen through the ranks – having been so incompetent at his job – without the wilful ignorance of those higher up…

3. Did Osborne collude with Buckells in Gail Vella’s murder?

During Buckells’ interrogation, AC-12 put it to him that the OCG didn’t actually order Gail Vella’s murder as they had no real reason to. The only connection they had to her on their side was through Tommy Hunter – who is long dead – and his son Darren (who was one of the gang who attacked Lawrence Christopher), who Fleming noted was a “nobody” to the OCG. 

However, two police officers now involved in the original Christopher investigation are now high-ranking – Buckells and Osborne – meaning they had the most motive to want her dead, as she was beginning to establish links that proved institutionalised corruption in the force.  

Buckells never answered the question as to whether he colluded with Osborne to have Vella murdered, but it would be likely that Buckells called in a favour from the OCG for Carl Banks to carry out his dirty work. 

While we don’t know for certain that Osborne was involved, he has a history of corruption, extending right the way back to series one, when he covered up what happened in the killing of Karim Ali.

The pre-credits sequence also told us that “close colleagues” of the Chief Constable have been appointed to senior positions in anti-corruption, with AC-12’s powers to curb wrongdoing in public office never weaker, which suggests he is suppressing information. 

4. Will Buckells get off?

It also seems like Osborne and Carmichael want to help Buckells get off, despite the case against him appearing pretty water-tight. 

The pre-credits sequence informed us that Central Police has submitted an application for public-interest immunity in legal proceedings against him, which means that if it is successful, no evidence about institutionalised corruption would be heard in court. 

This suggests they don’t want him to face justice as it will expose something much larger…  

5. Is DS Lomax corrupt? 

We have a feeling that if Line Of Duty does return, we’re going to be seeing a lot more of DS Chris Lomax. 

We still do not know who forged the production order for Davidson’s interview at Hillside Lane, and everything is telling us that it has to have been him. 

Arnott inadvertently revealed to Lomax that AC-12 were looking at Osborne in relation to the fourth man, and the next thing we know, Buckells has ordered Davidson’s murder. But Buckells had to have colluded with someone to get the production order arranged – and given they used to work together, this could have been Lomax. 

We also still haven’t forgotten the seemingly innocent line about being “in the Red Lion” from episode six, which hinted at his OCG connections. 

Plus, Lomax was also looking pretty shifty at the end of the episode when Darren Hunter was being walked to his cell – which could support the fan theory that he was one of the youths who attacked Lawrence Christopher. 

6. What happens to Fleming next?

Fleming was seen visiting the medical officer after she’d a candid chat with Arnott about his addiction, and we’re not really sure why. She could have just decided to check in with a professional after the traumatic events of the last few weeks, or there could be something else going on with her that we haven’t seen. 

Fleming also hinted to Arnott that she would return to AC-12 as long as Carmichael was not in charge, but with the DSC revealed to still running the department, Fleming might have decided to stay with the murder investigations team instead.

7. Why did Fleming flee the scene of Pilkington’s shooting?

Listen, we know we’re probably just going to have to let this one go seeing as there were no answers about this in the finale, but we just want to reiterate: We still don’t get why Fleming ran after shooting Pilkington and why Davidson took the rap for her. 

All six series of Line Of Duty are available to stream on BBC iPlayer.