Old age pervades the book, and what Rebus is going to do with his retirement is a major question. He knows little else besides police work and it obviously energises him. At the opening he's back working after having officially retired, this time for the underfunded cold case office which is due to be disbanded at the drop of a hat. He's also considering reapplying for the force but he's hounded by Malcolm Fox, the main character from the two Complaints books (who appears here rather differently, since we're not in sympathy with him particularly and Rebus certainly isn't). Fox is out to get Rebus, the man who's broken so many rules in the past, but Rebus is always too wily, too old-school for him.
The story mostly concerns a missing girl, who may have been murdered. It's a case Rebus should never have taken on; indeed, he only comes across it by accident, and it's almost by accident that he stumbles across the possibility of a serial killer at work, and the consequences of what that brings. Rebus has a knack for going outside the boundaries, for insulting people with wit and insouciance, for mentoring Siobhan Clarke, his young police companion from many previous books, even though she's never quite sure if his style of mentoring is satisfactory. (Fox definitely doesn't think it is.) He can undercut authority without blinking and keeps the pompous in their place. He's a rich character and it's not surprising Rankin has given him yet another outing after implying he wouldn't write any more books about him.
There's an enormous amount of chasing around the countryside in this one - Rebus, in particular, spends a lot of time on the road following up hunches - and Rankin delights in describing the nature of the different areas, in describing the traffic snarl-ups and the queues and the road works and the huge trucks getting in everyone's way. He plainly has a love-hate relationship with Scotland and its traffic. You almost need a map beside you to keep tabs on all the shifting scenes. In fact it might help to make more sense of how much driving Rebus actually does, sometimes alone and sometimes with others and where he's going. Maybe I'll do that next time I read the book!