This is probably my favorite so far, and although it is the fifth book by publication date, the events take place at the end of the first book, when things are getting rather dangerous for Holmes and Mary and Mycroft offers to send them out of town. Mary has always wanted to visit Jerusalem, so Mycroft sends them to British-controlled Palestine where they are embroiled in a series of murders and led by two Arab men who have a really hard time with a capable woman who can pass as a man when the occasion calls for it and is every bit as capable (if not more sometimes). As they work their way to Jerusalem chasing their adversary, they run into danger, prejudice, violence, politics, and intrigue, even while Mary shows her male skeptics just how capable she can be. Definitely my favorite Mary Russell book so far!