April 1861. Lieutenant Jedidiah Tremblant of the Illinois State Militia is riding the rails under orders of his governor to coordinate with the War Department in Washington, D.C. Arriving in Baltimore on April 19 th , Jed is shocked to find the city in the midst of a riot with its citizens attacking Union troops traveling through the city. In the space of that fateful day, he discovers that one of his fellow passengers is a southern spy, running guns to the southern sympathizers. He also witnesses a murder of a young Union officer by that spy and takes on the responsibility to care for the officer's newly-married wife, Maura Harrison, who had been accompanying her husband. Rather than be left alone in Baltimore, Maura convinces Jed to let her go with him to Washington. At the War Department, Jed and Maura have a chance meeting with President Lincoln. Disturbed by the riot and Jed's repost of the gun-running, President Lincoln enlists him to be his agent in Baltimore. Maura, after a private conversation, convinces the president that she should go with Jed, over both Jed and the Secretary of War's objections. Can Jed and Maura thwart the plans of the secessionists? They have to deal with powerful politicians, murderous militiamen, secret weapons, and glory-seeking generals, along with the Confederate spy, all seeking to put Jed in an early grave.