The eighteenth novel in the “Kaitlyn and the Highlander” series is “Time Is a Wheel,” written by Diana Knightley. It centers on Magnus, who meets a new foe who was born in the past. Whether time is a wheel or goes in a straight line is important to the narrative. Magnus must maintain the timeline’s accuracy while dealing with fresh foes and outdated scorecards. It’s a modern romance with a hint of science fiction and history.