Line of Duty, episode 3, review: Who knows where this convoluted plot will go next?

We’ve come a long way from ’ello ’ello ’ello. The fifth series of Line of Duty (BBC One, Sunday) is determined not  to rest until every member of the thin blue line is exposed as a wrong ’un. Bent, corrupt, on the take, up to their neck in it – you name it, all bobbies  are at it. When the gang planned  a raid on a police depot, Ted Hastings (Adrian Dunbar) wondered if they had backing from a panzer division. It’s not beyond the realms, is it?

This episode explored the idea of two missionary detectives who might have been separated at birth: DS Steve Arnott (Martin Compston) and his short squat combustible doppelg?nger John Corbett (Stephen Graham). Fierily committed to ultimate justice, behind each of them was a woman whose trust they flouted. The whole set-up had a neat symmetry until Arnott went and spoiled the promising plotline by ’fessing up to DI Kate Fleming (Vicky McClure). It was rather harder to credit the gullibility of Lisa McQueen (Rochenda Sandall) who spent the episode side-eyeing and swallowing Corbett’s baloney.

Anyway, we’ve now got a definite lead on the identity of “H”. He (or she?) can’t spell. “Definately,” he (or she?) typed in that anonymous computer link. Tut tut. It’s something to go on, or it would be if Corbett weren’t ignoring such vital clues as he speed-morphed from cool-headed UCO into human IED.

Is it Hastings? We don’t know if he can’t spell, but we do know that he’s hopeless with money and women and therefore vulnerable to the siren lure of the dark side. Gill Biggeloe (Polly Walker), all eyelashes and sarcasm, was teleported from Dynasty in a bad week for romantic sub-plots: DS Sam Railston (Aiysha Hart) picked the worst moment to grab a little us-time with Arnott. An associate of DCS Hargreaves (Tony Pitts), who was this week’s haemorrhaging casualty after being shot by Corbett, she’s probably bent too. With Corbett seemingly now losing his grip and heading for jail, quite what he intends to do to Hastings’s ex-wife is anyone’s guess.

There are three hours left for the plot to go any which way. It’s growing so convoluted that Arnott and Fleming were reduced to this more or less verbatim exchange.

Arnott: “Boss, I’m about to tell you what just happened in the Eastfield depot raid.”

Fleming: “Mate, as you know I already know, but spell it out for the viewers.”

Arnott: “If we talk fast it’ll look less like a blatant bit of exposition.”

Fleming: “This plot’s getting so knotty we’ve had to deploy  a DDSN notice.”

Arnott: “Like I always say, Dial Down the Serial Numbers.”