Line of Duty episode 3: Who is controlling Jo Davidson? Who is the ‘fourth man’? Is there something fishy about Chris Lomax? Is this the final season of Line of Duty?

Anyone complaining about the slightly slower pace of Line of Duty season 6 will have been left with egg on their face after episode 3, which felt like a greatest hits sequence from the show.

From PC Ryan Pilkington’s high-octane river crash and dastardly murder of an innocent officer to a sequence of shocking reveals – Steve and Steph! Ted’s cash! Farida attacked! Buckles arrested! – it really did feel like we were sucking diesel this week.

As far as AC-12 are concerned, they believe they may have got the Hillside Station leaker and corrupt officer in Buckells (Nigel Boyle). But we all know he’s been framed and set-up by Jo Davidson.

But what else did we learn in this evening’s episode? Here are our latest Line of Duty theories and burning questions…

Who is controlling Jo Davidson?

At the end of the episode, we saw Kelly Macdonald’s character on a laptop talking to the OCG using the same computer programme we saw Lisa McQueen (Rochenda Sandell) using in season 5.

All we needed to see was the misspelt word ‘definately’ on the computer again and we would have screamed.

Davidson is taking orders and cleaning up the mess for the OCG and the ‘Fourth Man’ (‘H’), but what hold they have over here isn’t clear.

On the basis of her high-security flat, she lives in constant fear of what they might do to her, but she’s so far been smart enough to follow their orders and place others (Buckells, Farida) in the frame for her actions.

One wild theory online is that Davidson is the half-sister of John Corbett – a viewer believes that the picture of her mum in episode 1 matches with John’s mother Anne-Marie McGillis (see below) – and that Davidson is tricking the OCG to bring them down from the inside.

It’s a fun theory, but if that was true what would be end game? Identifying the top dog and Fourth Man ‘H’ perhaps? It feels pretty far-fetched, but it might explain why Steph Corbett has had such a big role this series.

Is there anything rascal Ryan Pilkington won’t do?

We suggested last week that PC Ryan might be the show’s sneakiest weasel of all time and the latest episode might have been his crowning glory.

Murdering an innocent officer and attempting to bump off poor old Terry Boyle, is there anything rotter Ryan won’t do to keep his OCG chums in business.

Unfortunately for Ryan, his attempts to clean things up has only created more problems for him. Kate and Steve have dug out his old files and now remember him from the days when he was trying to chop off their fingers and stealing burner phones. How long will they leave him hanging before they reveal that they’re onto him?

Why don’t we trust DS Chris Lomax? Could he be the new caddy?

We mentioned last week how Perry Fitzpatrick’s character could swing either way on the bent copper scale, but we’re definitely in the ‘he’s up to something dodgy’ camp after episode 3.

Not only does he have his snout in absolutely everything going on at Hillside – he was always taking the calls from Jo and Kate when they were out and about - but it also felt very odd that he didn’t background check the witness who tried to pin the blame on Terry Boyle.

He was more than happy to do the check later for Kate, but why did it take her prompting him to look into it?

His behaviour is reminiscent of ‘Dot’ Cottan and we suspect he could be the new caddy/man on the inside for the OCG. Maybe all those shots of Buckells cleaning his golf clubs are a red herring to throw us off the scent of the real bent copper in the team.

Is Buckles involved at all?

He’s definitely guilty of insensitivity, crassness and being a rubbish police officer. But the brashness of Buckles suggests that he might not actually be guilty of anything beyond incompetence.

Jo Davidson has planted evidence in his car and slowly dripped info to AC-12 and Kate that has got him arrested. But it currently looks like he's just a fall guy for the OCG.

Even the fact that Buckells got Ryan Pilkington the job in the team doesn’t necessarily make him part of the criminal activity. The hapless boss could easily have been leaned on to give Ryan the role and we don’t suspect he’s the most conscientious man, so he could easily have just fast-tracked the appointment as a favour.

Who was Jackie Laverty?

She was only in the first season of Line of Duty, but Gina McKee’s Jackie Laverty comes up time and time again in the show.

This week, Ted Hastings and Steve Arnott finally discovered what happened to her body as the DNA from Terry Boyle’s fridge was matched to Laverty.

You could be forgiven for forgetting who Laverty, but her corpse has come to hold quite a large significance across the six seasons of Line of Duty.

In season 1, she was the secret lover of DCI Tony Gates and a criminal associate of Tommy Hunter. When she was murdered by Tommy Hunter’s gang, they blackmailed Tony Gates and made him look like the killer.

The OCG kept her body in the fridge of Terry Boyle to hide it from the police and it remained there ever since. It was even mentioned in season 5 when the OCG returned to Terry’s flat to spy on the print shop used by John Corbett.

The fridge finally had to be moved for season 6 as the police prepared to raid Terry’s flat, but it was ditched in a hurry and AC have tracked it down along with Laverty’s DNA. The connection between Boyle’s flat and Laverty means that Hastings and Arnott have proof this new investigation involves organised crime. Something Jo Davidson had been doing her best to avoid investigating.

What was the cash in Steph Corbett’s attic?

Another season of Line of Duty, another ill-advised romance for dirty dog Steve Arnott. His back may still be giving him some serious jip, but at least he can still cut it when it matters in the bedroom. The women just love a swish waistcoat.

Steve and Steph finally took their relationship into the bedroom and shared a few confessions over pillow-talk. Steve also took the opportunity to search Steph’s house the morning after and discovered in the roof, the big brown envelope of dirty cash that Hastings secretly gave Steph in season 5.

Hastings gave Steph the cash because of guilt he felt over the death of John Corbett’s mother, who Ted used as an informant in his early years. And possibly because of his own role in John’s death in season 5 - although it was never confirmed whether Ted was truly to blame for blowing John’s cover.

Are Ted and Steve on a collision course?

Steve knows about the cash in Steph’s attic. Hastings knows about Steve’s drug problems. This isn’t going to end well.

Is this going to end the careers of both men? Will they be able to use the information they have on the other to keep everything silent?

We’re worried that Steve is going to serve up Ted as the potential ‘fourth man’ and ‘H’ all over again and we’re not sure our hearts can take it.

Who is the ‘fourth man’?

Ted Hastings was warned again this week to stop chasing ghosts and stop causing trouble with the Gail Vella investigation.

But Hastings looks determined to use his final roll of the dice to bring to an end the corruption at the top of the police force, regardless of the consequences for him.

The central mystery remains, who is the ‘fourth man’ (or woman) pulling the strings.

Sindwhani (Ace Bhatti) and Andrea Wise (Elizabeth Rider) are both doing their best to shoot eyes at Ted and make themselves look guilty as sin. The other big contender is Own Teale’s Philip Osbourne, who last appeared way back in season 1.

Back in season 1, Osbourne was the leader of the Counter Terrorism Unit who bodged and covered up the inquest into the shooting of Karim Ali.

Despite a confrontation in season 1 with Arnott, Obsorne has managed to keep climbing the ladder and is now the Chief Constable.

We’ve also seen footage of Osborne and Sindwhani being interviewed by Gail Vella in uncomfortable circumstances. Both men would have plenty of reasons to want the journalist bumped off.

Will this be the final season of Line of Duty?

With all the throwbacks to season 1 and the mystery of the ‘fourth man’ feeling like its coming close to a conclusion, it looks like Jed Mercurio is at the very least positioning season 6 as a possible ending for the show.

Line of Duty could always return with new stories and more bent coppers. But at some point Mercurio or the BBC may make the call that the series has reached its natural conclusion. If it does end after season 6, episode 7, at the very least it feels like we’re going out with a bang and some definitive answers to the show’s long-running mysteries.

Watch Line of Duty season 1-5 and the latest episodes in season 6 on BBC iPlayer.