Spiral, Series 2, BBC Four

Though our French cousins like to boast of their superiority to the Anglo-Saxons in every sphere of endeavour, the Paris-based police dama Spiral, returning after a three-year absence, suggests that the Cartesian paradise across the Channel is under siege.

Already, it’s clear that the ghoulish murder that opened this first episode of series two has triggered an examination of the interplay of police, politicians and judiciary which threatens to uncover hideous secrets in the loftiest eyries of the French establishment.

You could say that Spiral’'s subject matter makes it a kind of Gallic Law & Order, except that it resolutely avoids the latter’s cut-and-shut formula of “that was the police investigation, and we’ll be back after the break to see what happens when the accused goes to court”. The French title is Engrenages, which means “cogs”, alluding to the way every aspect of the narrative is inextricably enmeshed in the bigger picture.

The story so far focuses on rapper and drug profiteer Aziz, who we first meet as he chastises a customer who has fallen in arrears by locking him in the boot of a car and setting fire to it. The police, led by Chief Inspector Laure Berthaud (Caroline Proust), tramp around the Parisian housing projects looking in vain for witnesses among the Arab population (what they don’t know is that a young kid videoed the killing on his phone, but for now that’s left ticking away in the background.) They drag the charred corpse back to HQ for a nice bit of pathology, but there isn’t a lot left for the medical examiner to work with. Then the cops begin looking into another case involving Adrien, a teenage drug dealer who’s selling heroin to his schoolmates, and this seems to offer a route into a trans-Parisian narcotics network which, we may infer, will involve Aziz.

That’s just the plot, but Spiral really starts to grip when it starts exploring how the echelons of power and contrasting personalities within them interact. Down at the courthouse, flame-haired human rights lawyer Josephine Karlsson (Audrey Fleurot) seems to be flying the flag for the repressed and downtrodden, so it’s a jolt to see her accepting a generous cash bung from a Croatian wife-beater she has successfully defended (“it’s traditional to beat a woman!” he protests). Then she energetically defends the bile-spitting thug Kevin, arrested after attacking Inspector Berthaud, portraying him as a “simple soul” traumatised by outrageous police brutality. He helpfully signposts his non-existent injuries by wearing a neck brace. Berthaud is disgusted by Karlsson’s blatant career-mongering, and you start to get a sense of why the policeperson’s lot must often feel like pushing a grand piano up the Eiger.

That’s barely the half of it. When the police raid the luxurious apartment where Adrien lives with his parents, and find his stash of drugs hidden in the fireplace, it looks like a straightforward case until his father’s lawyer, M. Vidal, starts pressurising prosecutor Pierre Clement (Gregory Fitoussi) to drop all charges. Clement demurs, until Vidal silkily invites him to dinner with a cabinet minister to explain his position. Acutely conscious that career ladders can lead down as well as up, Clement is promptly on the blower trying to get Adrien out of jail.

All of which adds up to a dispiriting reminder that “justice” isn’t a product of unambiguous facts inscribed in black and white, but more likely a teeming swamp of bribes, prejudices, lies, ambition and political expediency. A treacherous spiral indeed.