An Internet troll, a wide-eyed technical entrepreneur, a little-known Civil War general’s autobiography, theft of classified information, and a pack of gray wolves. They all have parts to play in a Mac MacArthur tale that stresses the need to keep your promises. Mac, Jenn Langton, Andy Patel, Jeri Klein, and the German Shepherds return to Ann Arbor’s technical frontiers as another in Joe McConnell’s trademark mysteries unwinds.