This is book 2 of the "Matthew Fox" series.

This note contains spoilers for the book.

Police procedural, set in Scotland.

The protagonist is in "The Comlaints", what we'd call "internal affairs" here, the people who go after crooked cops. Only slightly more popular over there than they are here, if fiction is to be believed.

A case they're called in on sends tendrils out in all sorts of strange directions, including backward in time. Some of this has a bit the feel of Anthony Price's novels, the way current events are influenced by the past, and the way people change. In this case it involves mainstream politicians who have pasts of political extremism, including terrorism, in their college years.