Strike: The Ink Black Heart, BBC One review - protracted, convoluted puzzler lifted by its leads

The man whose name sounds like a major aviation accident, private detective Cormoran Strike, is back, with his sidekick Robin, for more of the lobster quadrille that is their relationship.

This sixth series still uses those classy credits – footage of the leads in faded 1970s browns, with a typeface straight out of movies of that era and overlaid with Beth Rowley’s intense lyrics “You and me, me and you… I’ll walk beside you.” What follows is all too familiar as well: a dark new case that’s long-windedly puzzling and taxing. Ditto the pair’s continuing inability to declare the deep feelings they have for one another. Snafu.

With classy actors like Tom Burke and Holliday Grainger playing these potentially intriguing characters, you hope for more. In fact, these are the only two rounded characters in the series. If their relationship doesn’t deliver, what’s left is The Plot, and the vast cast shoehorned into it. 

It begins simply: Edie (Mirren Mack), a troubled young woman, seeks Robin’s help as she is being trolled and the police can’t intervene. Then she ends up dead, handily in Highgate Cemetery. She and her ex, Josh (Jacob Abraham), wounded in the attack, once created a cartoon about a creature called the Ink Black Heart. Now the cartoon’s film rights are about to be sold and, gasp, human actors will be used. The fans are not happy. Especially the ones who meet on a site somebody has created that’s based on the cartoon, Drek’s Game.

One player there, a red-hooded, levitating type called Anomie, is possibly the stalker/murderer. But as suspects, he/she/it is joined by a faction of ultra-far-right terrorists with Norse rune tattoos (pictured above); Pez (James Nelson-Joyce), a Scouse artist and naked life-class model; Katya (Emma Fielding), who mothers Josh rather than her own two children and disabled husband (Christian Mackay); Kea (Ellise Chappell), Josh’s ex, who has accused Edie of plagiarism; Edie’s gammon uncle, Grant; her creepy new fiancé... Soon a big pinboard of likely suspects who stand to gain from the rights sale, as well as those bent on stopping it, is up and running in Strike’s office.

But it’s not much help in keeping track of this vast cast, whose names are rattled off, sometimes semi-audibly, as the plot motors on. The viewer can’t go back a few pages to double-check who they are (is this a wheeze to sell more of the books?). Many of the suspects also have handles, their online player IDs, so that’s more information to process. Strike attempts a convoluted theory in episode 3, juggling all these names until I honestly gave up following. 

Slowly, though, the suspects’ pics on the board have Post-its stuck to them, indicating they are not Anomie. Or are they? Is the word anomie a clue? The script usefully inserts a reference to it for Robin to define: a lack of the usual social or ethical standards, often brought on by insufficient social contact. Here it could be applied to the terrorists, or even to the online world, where ”socials” can turn remotely conducted relationships into cruel and violent ones. Or is this a dig at the taciturn Strike?

Bobbing up and down in all this scripted flotsam and jetsam, Cormoran limps along with his increasingly painful Afghan war wound, and Robin rebounds cheerily from her short-lived marriage and divorce. The storyline also lobs in Cormoran’s ex, Charlotte (Natasha O’Keeffe), who's thrashing out a divorce settlement of her own with sadistic cad Jago (Pip Carter) and is now circling back for Cormoran like a dogged U-boat. Meanwhile, an attractive detective (Stephen Hagan) starts cosying up to Robin. And invisibly, Cormoran also acquires a girlfriend, who just as invisibly disappears, as if Tom Lodge, the writer, had an afterthought. Maybe he, too, couldn’t work out where Cormoran could have found the time for a sex life.

Thank goodness for Ruth Sheen (pictured right), the veteran Mike Leigh collaborator, who plays Pat, Strike’s office manager. Her rock-steady savvy and crabby wit provide a running commentary (some of it silent, achieved with a firm stare) on her boss’s lack of sense, especially where Robin is concerned. Robin also has a confidante, sensible Ilsa (Caitlin Innes Edwards), there to nudge along our understanding of what Robin wants. Which is “definitely” not to be in love with Cormoran. So the two of them are made to dance around each other, he with the expression of a doleful puppy, she succumbing to tender pangs when she sees him in pain and vulnerable and in need of a blanket. 

After five series of this titillatory routine, you might reasonably expect this partnership to be getting somewhere. But Robert Galbraith (Rowling) is operating in genre-fiction territory here, where no end to this story arc needs to be in view; quite the opposite. The couple’s prolonged romantic pain is her gain. 

It becomes clear that the viewer is being asked to become ensnared for four hours in a constantly moving plot mechanism. Part of the pleasure of the detective genre is its formula, being swept along by events you don’t understand but know will be explained before the closing page by a leading man who will live on to front the next instalment. But here the genre mechanics are irritatingly blatant, the large cast lightly sketched in because what happens to them may be essential but their unique personalities aren't. Even the leads have to become cogs when the drama’s mechanics demand it, as in the final episode, where Anomie’s identity is established with at least 10 minutes to go, but kept secret from the viewer – and no-one in the know reacts by uttering the name in question. As if.

What keeps you watching, inevitably, are the performances. Burke can convey mercurial shifts in mood that pass over his hangdog face like fast-moving clouds; his faltering attempt at a rueful smile in the final scene is a bewildering volley of quick-change expressions. He makes Cormoran’s despair at his increasing lack of mobility feel genuine and heartfelt, unhappiness that Grainger bounces off, a possibly too positive thinker who lights up her investigative playacting with big smiles but may need to be rescued, even by a limping man. She has, though, an emotional intelligence he knows he lacks. 

Cormoran gives us a glimpse of his actual psychological depth when Robin asks him why Charlotte married the grim Jago: his reply could be describing her and her grim accountant fiancé. But that’s the only significant twitch of the curtain the script allows, until the next series. And even then…

• Strike: The Ink Black Heart is available on iPlayer
• More TV reviews on theartsdesk