The wait for Rebus’ return was not as long as Holmes’ from the Reichenbach Falls. Only a year after the Edinburgh detective ‘retired’, readers were reassured he would return, and he did, working cold cases. Now he’s back on the front-line, in a neat role reversal detective-sergeant to former protégée Siobhan Clarke’s detective-inspector.

Malcolm Fox is back too, on his last case with ‘The Complaints’ – the police’s internal investigation department – before he moves back to CID, working with those he’d investigated for corruption, not a happy thought. He gets a taste of what this will be like as he attempts to co-opt Rebus to turn over his old colleagues.

When Rebus began his career, Summerhall nick was dirty from top to bottom: witnesses suborned, blind eyes turned, violence and intimidation working-tools in keeping the streets clean, or so the self-named Saints of the Shadow Bible – Summerhall’s detectives – told themselves. A 30-year-old murder case is now reopened: did it and the murderer walk with police complicity?

Meanwhile DI Clarke is dealing with a road accident. University student Jessica Traynor drives off the road one night and crashes. But she’s a careful driver, there’s no visible reason for the smash. Why make it complicated, urge not only her wide-boy financier father, and her boyfriend, the son of the Justice Minister, but also Clarke’s superiors, too.

That is, until the minister himself is assaulted.

Where does loyalty lie, is the question that permeates the book. So many loyalties owed by and to so many. How do they get balanced, who is owed what, past or present? This is what Rankin does best, complex multi-strand plots that interweave to elaborate a theme.

In their earlier outing, Fox and Rebus had a fascinating Jekyll and Hyde interaction, Fox, a teetotal pencil-pusher, is a flipped photograph of Rebus: what he might have become, if he’d taken another road. Here, however, they draw closer as they work together, and the nuances flatten.

In fact, Saints sometimes feels more like a sketch than a finished novel, despite its length, the author relying on our knowledge of the previous books to gesture at, rather than depict, characters.

Rankin’s technical mastery is renowned, and rightly, but here he allows Clarke and Rebus to spend two pages bringing the reader up to speed by telling each other the backstory of the Summerhall murder. At another point, a character is told, ‘If you worked there as a detective at that period, you were a Saint of the Shadow Bible’. An on-his-game Rankin would never have let that stilted ‘of that period’ stand.

There is, altogether, a sense that the author just wasn’t paying attention. One plot element is explained twice, another character is introduced with a cursory ‘I looked him up on Google – SNP stalwart…face of the ‘Yes’ campaign…married to a lawyer called Bethany.’ Rankin has always been good at not over-explaining, letting the reader fill in the blanks, but it’s a fine balance, and a Google search and a scattering of ellipses falls thumpingly down on the wrong side.

And then, just as you think you’ll give up, along come reminders of why Rankin, and Rebus, take their place at the head of the pack. A brief phone conversation between Rebus and a colleague is so tight, so efficiently written – and so funny – that you fall in love with the series all over again. It ends with a text from a desk-sergeant: ‘Blow me,’ it says, in its entirety, and then the masterstroke: ‘followed by three kisses’.

On balance, then, xxx, and add the novel to your Christmas list.

Ian Rankin, Saints of the Shadow Bible (Orion, 428 pp.)

First published in an edited form in The Times