May 1144. Newly wedded, Gareth and Gwen travel across the border into England on a diplomatic mission with Prince Hywel of Wales. Within moments of their arrival, however, the mission goes awry and a murder case drops (literally) at their feet. Hindered at every turn by a climate of civil war and constantly shifting political alliances, Gareth and Gwen race to solve the murder and expose a plot that threatens not only their lives, but the life of the future King of England himself. Murder, intrigue, and treachery take center stage in The Fourth Horseman, the third Gareth & Gwen Medieval Mystery.