Across the River - Books of Furnass, #4

In the summer of 1863, Judson Walker, a captain of Morgan's Raiders, and Jonathan Reid, a young engineer, come to Furnass to appropriate two of Colin Lyles' steam-powered road engines. The purpose is to outfit the engines with iron plate and the newly developed Gatlin Guns, and, with Morgan, deliver the war engines to General Lee's army in Central Pennsylvania. Amid Walker's growing involvement with Lyle's wife Libby, deserting soldiers, and Reid's own agenda, Walker learns Morgan isn't coming.
The novel reaches its climax with Lyle trying to sabotage the war engines. Walker must decide between Libby and duty toward his men, the war and individual human values.