This historical novel is about the Civil War. On June 29, 1863, a spy returns from a mission to an officer named Longstreet with information of the Union's whereabouts. The intel means General J.E.B. Stuart isn't tracking the Union as planned. He plans to go backwards and around, going south through Gettysburg before turning north to intercept the Union.
The Union is not without confusion either. South of Gettysburg, Col. Joshua Chamberlain tries to manage his new additional soldiers, a hundred men from another outfit that defected to him. The Union cavalry holds Gettysburg under Gen. Buford's charge. He realizes that because of the positions of the armies, a battle at Gettysburg is becoming more and more likely by the day. He sends his 2,200 troops into the surrounding hills, making sure that the Union has the advantage of height all throughout the countryside. For a moment, the narrative cuts back to Longstreet, helping plan the infiltration of Gettysburg.
On July 1, General Lee bemoans the missing intelligence that Stuart was supposed to bring. He is going into conflict blind. Longstreet explains his strategy to the General, to swing southeast before going north to intercept the Union's main forces. Lee rejects his counsel, saying that victory will come in one single, decisive battle, not in a long series of defensive maneuvers.
In Gettysburg, the two armies are in combat. Buford's forces hold off the Confederates from invading the city until General Reynolds assumes control. He is killed not long before General Lee arrives to aid the Confederates. The Union retreats to the hills where they set up defensive measures, like cannons and stonewalls. Both camps end the first day with serious discrepancies among leadership. Buford is blamed for the loss of Gettysburg.
The next day, Chamberlain continues north to Gettysburg, thinking to himself about race, racism, and slavery. The Confederate camp is still stuck in conflict about strategy. Lee likes the more aggressive plan to attack the Union's flanks, but Longstreet is sure that they should continue toward D.C. Longstreet loses and has to flank the Union anyway. He finds that they are not in the hills, but right in front of him in the peach orchard, and the armies engage each other. Many die in this battle.
Chamberlain arrives as the last line of defense, so he can't retreat. His army defends well, but soon, they're out of bullets. They bayonet charge the Confederates, who flee, scared by the army's screaming and charging. When Stuart arrives at the Confederate camp, he is scolded by General Lee. Lee plans to attack the Union in the center, split their forces in two. Chamberlain is moved by the Union to the center in an attempt to let his strained soldiers rest. Longstreet agrees to head the charge through the middle.
The Confederates engage the Union with artillery, hoping to knock out the Union's own artillery. Chamberlain was led to believe there was no chance the center lines would be attacked, but he survives the artillery shelling. The artillery was aimed badly, so for the moment, the Union is fine. When the Confederates approach, they march right into cannon fire, and hundreds die, causing the lines to become disorganized. When they come close enough to hit with a bullet, the Union opens fire. Pickett retreats to Longstreet's command reporting 60% losses. The battle is over when the Confederate army retreats from Gettysburg.