The Green Man

This is the new Roger the Chapman mystery.
in the summer of 1482, an English army, under the command of Richard, Duke of Gloucester, invades Scotland in order to win back the border town of Berwick-on-Tweed and to put King James the Third's renegade younger brother, the Duke of Albany, on the Scottish throne. Albany insists that his old acquaintance, Roger Chapman, be a member of his personal bodyguard, so an astonished and extremely reluctant Roger finds himself, by royal decree, a part of the invading forces.
But during the march northwards, a series of sinister events, centred around the cult figure of the mythical Green Man, makes Roger question Albany's true motive for requesting his presence. And once in Edinburgh, he is called upon not only to solve a murder, again involving the Green Man, but also begins to realize that his own life could be in danger.