It's hard to stay retired, as John Rebus finds in this follow up to Saints of the Shadow Bible, his 20th novel (and Malcolm Fox's 5th). While DI Siobhan Clarke is investigating the killing of a former senior prosecutor during a robbery, a note is found that indicates this may not have been a random attack. Then semi-retired gangster Big Ger Cafferty receives an identical message, and Clarke decides they'll need Rebus's help if they want to save Cafferty's skin. But another crime family has just arrived in Edinburgh, and the undercover team tracking them enlists Fox. There's something these people want, and they'll stop at nothing to get it.