It’s always a tricky spot in lengthy crime dramas; a point where, between the initial momentum of the mystery, and the thrill of closing in on the conclusion, the plot can sag and you can feel cheated of 4 hours of invested viewing.

Fortunately Episode 5 of The Tunnel provides us with a nice tight episode, with enough action, death, detective work, and – say it quietly so the rest of the Internet doesn’t hear – sex, to stop you from flicking over to BBC Two’s Tudor Monastery Farm, where there’s no sex or murder, more’s the pity.

We begin as Benji wanders into a mental health clinic and chops off an unsuspecting doctor’s head (as if getting an appointment these days wasn’t hard enough for the rest of us) and, after killing two others, fails to kill himself. It’s the Truth Terrorist’s first big mistake, and Karl and Elise are quick to try and capitalise on it, especially as the life of 15 year old runaway and friend of Benji, Sophie, is in danger now that she’s seen TT.

Don’t let the urgency fool you though. There’s still time for Karl to have sex with the widow Joubert (careful love, the man’s just had a vasectomy) and for Elise to have some uncommital thrusting with Gael. It’s rather curious that the former is implied while the latter is explicitly shown, until you realise that it all serves a dramatic purpose by mirroring the motivations of the characters: Karl wants his indiscretion kept hidden, while Elise is almost disarmingly open and honest about sex. It’s a carefully crafted insight into their character’s motives.

In a series where truth and lies are the core of the killer’s motive, it makes you overly aware of the tangle of brutal truths and shallow lies that hold people and societies together. ‘One lie leads to another. How do you trust someone that lies to you?’ Elise asks Karl, suddenly highlighting the enormous canyon of candidness that yawns between them, despite their now more harmonious working relationship. They are the Yin and Yang of honesty. Karl Roebuck lies easily: ‘No love, I didn’t smoke’. Elise tells the truth without hesitation: ‘My English dinner is bland, bring me a bottle of Tabasco and a straw’. Only her past brings reticence.

And speaking of lies, when will the police learn never to trust a prisoner who says they need the toilet? Seriously folks, just keep them locked up and have a towel handy. Benji chomps down on a cyanide capsule and kills himself, thus placing the police back pretty much at Square Un. At least none of the constabulary are being kidnapped, like the gendarme on the other side of The Channel.

Well played, The Tunnel, you still have our interest. And that’s the truth.

Aired at 9pm on Wednesday 13 November 2013 on Sky Atlantic.

> Order The Tunnel on DVD on Amazon.

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