Paul and Alex Zunker find out soon enough that their Civil War trophy, a packet of letters, is a curse. It seems they are a "trigger" to a dimensional doorway that ushers in a procession of hideous supernatural manifestations that threatens the Zunker family, particularly Alex.

Later, after Alex is almost killed by the intruders in her room, she and Paul determine that the letters are responsible for what is happening to them. However, when they attempt to locate the letters to destroy them, the packet has disappeared. Now, they must find and destroy another "trigger" in order to close the deadly doorway.

Their quest to find this trigger takes them first to Northern Arkansas (where they encounter another, particularly viscious entity), and then to the haunted battlefield of Shiloh, where they come face-to-face with the full horror of Stehle's Door. Ultimately, it is Paul, the weaker of the siblings, who must face the full power of the fatal doorway and its deadly emissaries.