Marty is at the Brown's house. He's supposed to be studying for a test on the Civil War, but is instead playing his guitar. His video tutor has to shout loudly to get him to hear. She shouts the date, "February 11th, 1864!" The DeLorean's time circuits can now be voice-controlled, so this date gets entered as the Destination Time.
Meanwhile Jules and Verne are arguing over the use of the computer. Jules wants to use it for work, Verne to play video games. Doc says they should both go outside for a while, but Verne accuses Doc of always taking Jules' side. Upset, Verne takes the DeLorean. He doesn't notice the Destination Time is set for February 11, 1864. Verne arrives in 1864 and the DeLorean turns into a suitcase! This is Doc's newest invention, so the car can be stored. Unfortunately, only Doc's voice or Einstein's bark can turn it back into a car. Trapped in 1864, Verne has to join the Confederate Army as a drummer boy under General Tannen.
Back in present day Hill Valley, Jules discovers a picture of Verne in a book about the Civil War. His regiment was wiped out the next day in big battle! Doc, Jules and Marty use the train to go back to 1864 and bring Verne home. Marty guards the train but gets taken hostage, and Doc and Jules are taken by the Union Army, under General Clayton, Clara's uncle.
Next day, the battle begins, but Jules and Verne spot each other and try to protect each other. The armies note the brothers huddled up together in fright and realize they are fighting their own brothers, and the battle does not go ahead. Back in the present, Jules and Verne realize that fighting is not the answer.