Line of Duty series 3 episode 4 recap: Lindsay Denton kicks ass as the Caddy seeks to cover his tracks

Keeley Hawes’ convicted (but not connable) copper then punched him in a place where the sun don’t shine, videoing his blackmail and sending him out of her horrible halfway house digs with a kick up the bum.

Denton, who was released from prison in last week's episode, also reminded Robin of the likely sentence for his blackmailing. She may be cleaning floors in a supermarket but she hasn’t forgotten how to do her job.

You’ve got to hand it to her. She doesn’t take things lying down and in the dexterous hands of Keeley Hawes she remains a fabulous, compelling creation. I’m so glad she’s back.

Our Linds (as I now know her) didn’t take any rubbish from AC-12 either, paying a visit to the cops who incarcerated her and extracting every ounce of squirm from the encounter.

“I imagine they keep you very busy,” she quipped, cool as ice, to Polly Walker’s lawyer Gill Bigelow (what a name).

She also got her apology from Hastings and showed Steve Arnott up to his colleagues when she flourished a mobile recording which, she said, suggested they they had had intimate relations while he was investigating her in the last series. Her phone has come in handy, hasn't it?

But for the do-gooders of this drama her intervention actually had a downside. Kate Fleming (Vicky McClure) was so outraged that Arnott had broken protocol (and more importantly did not tell her what he'd done) that she propelled herself into the weasel arms of awful Mathew ‘Dot ‘ Cottan. After last week's cosy chilli together, the pair are closer than ever which can't be a good thing: Cotton, of course, is the cad who we (but nobody else) know to be the Caddy, the organised crime mole at the heart of the police force.

But while Cottan was revelling in his new-found position (he got a commendation last week for collaring Hari) and cleverly hinting to his bosses that the Caddy may be Arnott himself, it wasn’t all plain sailing for him. His failures to authorise key bits of forensics have been noticed by Arnott and he still has Morton (Neil Morrissey) on his tail.

The key final scene saw Dot breathe a deep sigh of relief as he believed his old friend had handed over all his incriminating evidence. (Did anyone else think Dot was going to plug him with the gun he had secreted into his flasher’s coat? I certainly did).

But we also saw that, rather sensibly, Morton has another phone with (presumably) the same evidence on it. It was a good moment, dramatically, but sounded the episode's only duff note of implausibility: why would he bring the duplicate phone to a meeting with Cottan? Why not keep it at home or in a safe place?

Anyhoo, elsewhere, we saw Hari admit to killing Waldron (though did he? I mean, did he really? Or has he been pressurised by Dot into 'fessing up? It’s impossible to tell.)

And the finger of suspicion hovers over Hastings. What was the handshake with Sandbanks suspect Fairbank (George Costigan) all about? Was it Masonic? Is he going to cover for him?

And why is he being so weird about his love-life – wining and dining Gill Bigelow (sorry, I still can’t get over that name) and then backing off just when they kissed?

Also, Bigelow (*chortles*) is pressurising him to get rid of Arnott. So with that and Dot dropping hints, a showdown can't be far off.

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Will Steve be kicked out of the squad, operating outside the team to get to the truth? You can’t help feeling that it will be between him and Dot from now on. And I’d like to see more of Joe, the Sandbanks victim movingly played by Jonas Armstrong. Maybe we'll see him play a bigger part in the final two episodes – perhaps in league with the disgraced but truth-seeking Arnott…?

It’s unbearably tense now as Steve seeks to ferret out more information while being shut out by his colleagues, one of whom is the arch criminal they are looking for.

I can’t wait for next week. Only two more episodes to go….