Among Civil War novels, this second effort by former U.S. Congressman Mrazek (after his prize-winning Stonewall's Gold) is a rare find: a book that successfully combines mystery, historical drama and impressive wartime verisimilitude. Lt. John McKittredge commands a company of Massachusetts infantry in the Union Army. A Harvard student from Maine, just 20 years old, he is eager and naïve about the war. Wounded at the battle at Ball's Bluff in October 1861, he spends nine months in a grimy, stinking military hospital where he becomes addicted to laudanum (opium). He survives his wounds and is assigned as an investigator with the Union Army's provost marshal in Washington, D.C. McKittredge buys laudanum on the black market while investigating cases of graft, bribery and theft involving fraudulent government contracts for shoddy military supplies and equipment. He is saved from an opium death by Col. Valentine Burdette, a disheveled and brilliant military policeman who sees value in the young officer. Together they pursue leads in a case of faulty munitions and gun carriages, an investigation that leads to the curious murder of a young woman and to crooked politicians and generals linked in a bizarre conspiracy to change the government and end the war. What McKittredge and Burdette do not realize until too late is that no one really wants them to solve the case at all, and that there are stronger powers who will kill to ensure they fail. Mrazek's portrayal of Civil War battle is stark, graphic, bloody and exciting, and is only exceeded by his memorable description of Washington, D.C., as a Gomorrah on the Potomac. Regional author tour.(Apr.)