The Sign of The Devil by Oscar de Muriel - and so I finally read the last book in the great Frey and McGray series, recommended on this very forum. In the 7th and final adventure, what seems to be at first a fairly straightforward case of arresting body snatchers turns out to be something more complex, as the two latest "victims" were both patients at the same asylum as McGray's sister, and both bore the so-called "mark of the Devil". McGray's obsession with his family's history goes into overdrive and when his sister is implicated in the deaths (which are at first passed off as natural causes) he will stop at nothing to protect her. And Ian McFrey, who thought he'd retired to his estate in Gloucestershire, agrees to come back to Edinburgh for one last case, which ends up putting him in more danger than ever. We finally find out the true connection between the McGray and Ardglass families, and it all leads to a thrilling conclusion - a great series which has been consistently good, and I am already sad to see that there aren't any more cases for our mis-matched detectives. 9/10