Mortal Causes

The motto of the Scottish kings runs through this one: nemo me impune lacessit, nobody provokes me unpunished, or as the title card might put it, don't mess with me. For Rebus it is less a motto than a job description. The trouble starts with the promise he made to Morris Gerald Cafferty after finding the driver who put Rebus's daughter in a coma. Now Cafferty's illegitimate son has been six-packed and killed, and Cafferty is calling in the favour.

What follows is Edinburgh at its most dangerous. Gun running, jailbreaks, nationalists, left- and right-wing extremists all spouting racist philosophy, and imported white-power fanatics carrying out hate crimes. The list is exhausting, and Rebus walks through all of it on Cafferty's clock. Every lead and locked door opens onto the same question: what does he owe, and when will the man come to collect. Rebus moves through the whole rotten assembly while owing the most dangerous man in the city a debt he cannot refuse.

James Cosmo is back as Cafferty, all polite menace, and John Hannah's Rebus knows exactly what he has signed. The cast around them includes Michael Nardone as DI Martin Kilpatrick, Michelle Fairley as Janice Mee, Kevin McMonagle as Frankie Bothwell, Ashley Jensen as Mhairi Henderson, Michelle Gomez as Caro Rattray and Paul Doonan as Davey Soutar. Sara Stewart's Gill Templer and Gayanne Potter's Siobhan Clarke hold down the police side. Ian Rankin and Mark Greig wrote it, and David Moore directed.

The episode is thick with plot, and some of it passes by too fast to register. The gun running and the jailbreaks blur together, and a few faces appear just long enough to be suspects. But the spine holds. Rebus owes Cafferty, Cafferty means to collect, and every corpse in between is a payment on the debt.

It is the show at its bleakest, and the bleakness suits it.