Here's what happened in Line of Duty's super-dramatic season 6 episode 5 – and all the questions we now have

1. Did Kate Fleming get shot – and is she dead?

MOTHER OF GOD. Is Kate Fleming dead? Kate can't be dead. But seeing as Jed Mercurio has a strong track record of dramatically offing major characters, we have to admit it's a very real possibility.

The episode ended with an armed standoff between DI Kate Fleming (Vicky McClure) and that little s**t PC Ryan Pilkington (Gregory Piper), while Acting DSU Jo Davidson (Kelly Macdonald) stood to one side, screaming. The screen then cut to black, there were two gunshots in quick succession, and then the theme music kicked in: DUN-dun-dun-dun, DUN-dun-dun-dun... and we'll have to wait till next week to find out who shot the bullets and where they ended up.

Ryan? Jo? Kate? Ryan and Jo? Ryan and Kate? Jo and Kate? Nobody at all? Hurt or dead? Did AC-12 make it to the scene in time? We've explored the cliffhanger ending from all angles in our in-depth article on who got shot in Line of Duty.

But there are a lot of other questions we need answered after a detailed-packed episode. Such as:

2. Why did Kate (apparently) trust Jo Davidson?

We've spent the whole of season six trying to work out what Kate really thinks of her boss, Jo. Was she going for drinks and making weekend plans with Jo just to gain her confidence, we wondered? Or was there genuine trust and friendship? (Maybe even romantic chemistry?)

And even if she did trust Jo before, would Jo's non-firing of Ryan in episode five be a red flag to Kate?

But then Kate agreed to meet up in an unlit lorry park for a private chat with Jo. Perhaps this was just Kate being incredibly, uncharacteristically naive: after all, earlier in the episode she insisted to her old boss Superintendent Ted Hastings (Adrian Dunbar) that Jo could be trusted, pointing out that Jo didn't call in the warehouse raid to the OCG, even though she was the only one on the MIT who knew they were raiding three locations.

Plus, Kate seemed to be caught off guard when Ryan got out of the car at the lorry park, even though Jo had just said "I'm sorry, Kate. I'm so sorry." You'd think she would at least reach for her concealed firearm at that point.

On the other hand, Kate isn't stupid. Perhaps she was actually relying on AC-12's surveillance tailing Jo and Ryan to the lorry park and catching them red-handed. "Why would she come here otherwise?" Jo commented, which is a very good question. Unfortunately, Kate had just been informed a few minutes earlier that those surveillance operations had been cancelled – and she clearly didn't fully trust Jo, because she made sure to text her location to DS Steve Arnott (Martin Compston). You wouldn't do that if you thought there was nothing to worry about.

3. What is the significance of Jo's family connection to Tommy Hunter?

At the start of this episode, we got the answer to the previous episode's big cliffhanger: yes, as RadioTimes.com readers predicted in our poll, Jo's mystery blood relative is Tommy Hunter (Brian McCardle). The crime boss was the head of the OCG in season one, and was killed at the start of season two.

"Davidson's DNA is a partial match for Tommy Hunter," Steve told Kate. "But that's not the worst of it. There's an unusually high percentage match for runs of homozygosity."

"Oh my God," said Kate. We felt the same, because we had no idea what he was talking about, and why that was "the worst of it". So we turned to the internet, which informed us that "runs of homozygosity" suggests they shared a recent common ancestor, i.e.they are very close relatives (maybe even father-daughter, though there are only 14 years or so years between them). From what we can gather, tots of "runs of homozygosity" could also mean that there was incest involved (!!).

But what are the implications of this family relationship?

At this point, there's still no clear explanation as to why Jo would work with the OCG. It doesn't seem as though she followed the same path as Ryan or DI Dot Cottan (Craig Parkinson) – that is, groomed and raised by organised criminals, and then deployed into the police force to make havoc. Rather, Jo seems genuinely distraught about having to work with the OCG; for several episodes, we've been wondering if she's being blackmailed in some way. She's spent 20 years working in the police force, but she seems very green about how the OCG operates.

Does the OCG have one of her family members captive, or something? How does the family relationship play in? And does this have anything to do with Tommy's son Darren Hunter, who got away with assaulting Lawrence Christopher in 2003?

4. What happened with the Lawrence Christopher case – and why did it get Gail Vella killed?

So, speaking of the above – we're finally getting some answers to the question of why Gail Vella (Andi Osho) was murdered.

Thanks to Steve's off-the-record chat with Jimmy Lakewell (Patrick Baladi) before his untimely death, AC-12 now knows what Gail Vella was looking into: the 2003 death in custody of a young black man called Lawrence Christopher. He was attacked by a group of white men and subsequently picked up by police, who left him dying in a cell of a head injury while they taunted him and made monkey noises as he died. Nobody was brought to justice for either the attack or the officers' behaviour, and the police investigation was badly mishandled (for which there were no consequences).

To most, it looked like a straightforward case of institutional racism: the police dismissing this as gang violence when Christopher was actually an architect with no gang links, and then dragging their heels on questioning witnesses and bringing in suspects. But Lakewell told Gail Vella to look deeper, saying: "Well it's got to be something pretty bad if you'd rather go with the story that you're basically a bunch of racists."

And what she found was that the police had additional motives for failing to fully investigate the death.

Because... Tommy Hunter's son Darren was one of the suspected killers! And Tommy was an OCG boss with powerful friends in the police. So the investigation had to be intentionally mishandled. The SIO on the case was a bloke called Marcus Thurwell (James Nesbitt), whose team included Philip Osborne (Owen Teale) and Ian Buckells (Nigel Boyle). Because of course it did.

Obviously, it would look pretty bad for Chief Inspector Philip Osborne (and Thurwell and Buckells) if any of this got out, which is a potential motive for them having Gail murdered.

But there must be more to the story – because Gail's murder was ultimately carried out on the night before she was meant to interview retired, disgraced, imprisoned Patrick Fairbank (George Costigan) in prison. What does he know about the Lawrence Christopher case, that someone was worried he would tell Gail?

Whatever it is that Fairbank knows, it may be tricky to get it out of him anyway thanks to his declining mental facilities. When Steve and DC Chloe Bishop (Shalom Brune-Franklin) visited him in prison, he seemed not to remember anything, or to know what was going on. Or perhaps that was just a bluff?

5. How does James Nesbitt's Marcus Thurwell fit in?

What is the connection between Thurwell and Fairbank and organised crime? That has yet to be fully established. But when Steve Arnott looked up Thurwell on the police database, he remembered why the name was familiar: Thurwell cropped up during a previous investigation into the Sand's View Boys Home scandal. His file is connected to Danny Waldron's and more. We'd previously heard him mentioned in passing, because he was a DI on Central Police's Vice Squad in 1998, and as an SIO on the investigation into the death of Oliver Stephens-Lloyd; however, this is the first time we've seen his face.

But Thurwell had retired and moved to Spain by the time AC-12 took an interest, so they didn't pursue him beyond sending local police to get a long-range shot of him at the harbour. Now, no one really knows where he is. But he must be important, because they've cast Nesbitt in the role rather than any old extra.

6. Is the Chief Constable the "big bad"?

We previously thought PCC Rohan Sindwhani (Ace Bhatti) and ACC Andrea Wise (Elizabeth Rider) were slimy creatures, colluding with the Chief Constable to thwart AC-12 and Ted Hastings at every turn. But Sindwhani has just resigned, and he now claims he was fighting AC-12's corner, against the Chief Constable. That's hard to fully believe – he's not talked to Ted like he was an ally – but it could be at least partially true.

So, if it's the Chief Constable who is ultimately trying to force through Ted's retirement, the AC-3/9/12 merger, and 90% staff cuts to all the anti-corruption units, that makes us think Osborne is the big bad; potentially even Ted's semi-mythical "H".

We knew he was a bad egg already: he covered up that police shooting in season one, when his men killed an innocent man in a botched anti-terror operation. But this bad egg now looks even more rotten, ever since we found out he was involved in the Christopher Lawrence case.

Also, we've now established he had a motive for wanting Gail Vella dead. The same motive also applies to Buckells and Thurwell, of course; but incompetent Buckells seems like more of a low-level rat, judging by the previous episode, while Thurwell is retired. Osborne is the one who seems to have the most to lose.

And then, just when AC-12 were making some progress, Osborne jumped the gun with the AC units merger and brought AC-3 boss Patricia Carmichael in to take charge and pull funding for all surveillance operations. Plus, he gave a bit speech in this episode about how politicians and everyone else should leave the police alone to do their jobs, which was highly suspicious. No oversight, please!

7. Is Carmichael bent?

Oh, Patricia Carmichael, how we love to hate you. Anna Maxwell Martin's character, who is the boss of AC-3, returned to torment poor Ted – and she enjoyed every minute of it. She barged right in to AC-12, announced the Chief Constable had put her in charge, and revealed that she'd cancelled AC-12's surveillance operations on Terry Boyle (Tommy Jessop), Ryan and Jo with immediate effect.

Carmichael's actions and her glee might be mainly about personal career advancement; the Chief Constable has put her in charge, and so she's happy to follow his directions (while also enjoying the chance to lord it over Ted, after the events of season five left her looking silly).

But the timing of all this seems very suspicious, especially as it threw Kate into immediate danger. Also, when she found Steve talking on the phone with Kate, she ordered him to hand over his phone – very menacingly indeed. And she wasn't keen on Ted, Steve and Chloe racing off to the lorry park to try and rescue Kate, either.

8. Who was messaging Jo and why did they spell it "definately"?

Never has a misspelling of a single word been so crucial to the plot of a TV drama. Yes, this episode saw the return of our old friend "definately". No, not definitely, definately.

The misspelling has cropped up twice before: once when the OCG was messaging with the senior police figure they presumed was "H", and he (or she) sent a message containing the word "definately". Then, it came up again when AC-12 had hacked the messaging system and Ted was pretending to be "H" in a conversation with the OCG; he also typed out "definately", a fact/coincidence which has never been satisfactorily explained (and which definately made us think he was "H" for a good chunk of season five).

And here it is again! The "unknown user" Jo has been communicating with on her home laptop – presumably a big crime boss or corrupt senior police officer – finally got quite chatty in this episode, pointing out that two OCG men had been killed at the workshop by AC-12 ("I recognised Lewis," wrote Kate), and ordering Jo to "get rid" of Kate Fleming immediately. "As long as it's my last job," said Jo, to which the unknown user replied "definately". Oooh!

9. What will Steve do now he knows why Ted gave Steph the money?

What do you do when you work for AC-12, and you discover your Gaffer ratted out an undercover cop and then paid his widow £50,000 of 'missing' OCG bribe money out of guilt? Steve doesn't have an answer to that question just yet. But in this episode, he finally put all the pieces together and work out why Steph Corbett (Amy de Bhrún) was hiding an envelope of cash in her attic, and why she was back in touch with Ted.

It was a visit to Blackthorn Prison which provided Steve with the final piece of the puzzle. While Steve was trying to get answers out of Lee Banks (Alastair Natkiel) by goading him about his dead brother Carl Banks, the OCG thug shot back at him: "You want to talk about rats? Ask your boss. He told me there was a rat in our crew. And that rat turned out to be an undercover copper. John Corbett."

For viewers, that 100% confirmed what we guessed happened in season five, when Ted went to see Lee Banks in prison. But for Steve, this was brand new information – and he was shocked. If Ted ratted John Corbett (Stephen Graham) out – perhaps in retaliation for John's attack on Ted's wife, or perhaps to try and bring him back in to the police fold by blowing his undercover mission – then that led directly to John's murder, whether he intended that or not. No wonder Ted slipped an envelope full of £50 notes to Steph Corbett, especially once he realised how John had been manipulated by Gill Biggeloe into going after him.

Anyway. The OCG's Mark Moffatt always insisted he gave Ted £100k, but so far Ted has successfully maintained he only ever received £50k in 'bribe money' (which he was never intending to keep). But Steve has now examined Steph's bank notes, and they're definitely from the same batch as the other £50k which the police confiscated from Ted's hotel room in season five.

Will Steve confront his boss? Or report his boss? Or let it go entirely? It's a big secret to keep, and so far he and Kate are the only ones who know.

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10. Why did Ted leave Ryan on the MIT?

Before, it was Ted who was keen to pull off Ryan off the MIT, for Kate's safety. Kate was the one to persuade him to hold off and leave Ryan embedded, so as not to alert the OCG that he'd been rumbled. But then, after things got even more dangerous and AC-12 was about to bring him in, Hastings did an about-turn. Why?

Ted's own reasoning does make sense. "We will be left holding a sprat when we should have been holding a mackerel," he announced. "He will lead us to the big fish." Mother of cod!

But while Ted has a point, what's strange is the fact of him suddenly changing his mind. Odd.

11. Is Steve ever going to make an Occupational Health appointment?

The fact that things haven't escalated any further than emails marked "urgent" is probably a good sign, but at some point Steve is surely going to have to face up to his inbox and book that Occupational Health appointment. That storyline about his back injury and painkiller addiction has to be going somewhere, after all.

Line of Duty continues on Sundays at 9pm on BBC One. Take a look at the rest of our Drama coverage, or check out our TV guide to see what's on TV this week.