A series of novels set in Scotland in the 1800s that follows the criminal investigations by two detectives. One (McCray) is a rough edged Scotsman with a bit of belief in the supernatural. The other (Frey) is an upper class Englishman. The two start out detesting each other but in spite of their differences and animosity they manage to work together to solve some very intricate crimes, each using their unique talents and brilliant minds. As the books progress they gain a mutual respect for each other even while still butting heads. Very well written and its evident that the author is very knowledgeable of the times and places. Also a rip roaring adventure!