On a ridge overlooking Burnside Bridge - the focus of the Battle of Antietam - souvenir hunters find the unmarked grave of an unknown Union Officer. Don Spaniel, an archeologist in the National Park Service, is called in to examine the remains. He soon discovers that the officer was murdered and that his identification disk could not possibly belong to him, since its rightful owner is buried elsewhere. Spaniel's obsessive investigation leads not only to his reliving the horrible carnage that occurred at Burnside Bridge over a century before, but to the true identity of the Union officer and the reason why another body resides in his grave in a small New England town.