Johnnie Gray has two loves: his engine and his girl. While he’s visiting Annabelle, Confederate troops fire on Fort Sumter and the War of Northern Aggression begins. Annabelle’s father and brother leave to be first in line to enlist, but Johnnie takes a shortcut and beats everyone in the crowd. But the army won’t take him: he’s too valuable as a train engineer. He tries a second time, claiming to be a bartender named William Brown, but the recruiters recognize him and throw him out. Annabelle’s father and brother see him and invite him to join the line, but he refuses and goes to sit on his engine, the General. They tell Annabelle that he’s a disgrace to the South, so she tells Johnnie that she won’t speak to him until he’s in uniform. He has only the General for solace.
A year later, a Union spy plots to steal the General and take it north, burning bridges and cutting off the Southern supply line in its wake.
At the Marietta train station, Annabelle says goodbye to her wounded brother as she leaves to take care of her wounded father. They both snub Johnnie. At Big Shanty, the passengers get out for dinner, except for Annabelle who checks on her luggage in the baggage car. Yankee spies steal the train and tie her up. Johnnie runs after it, then grabs a handcar. It soon runs off of the rails where the spies tore them up. Johnnie grabs a bicycle and continues his pursuit.
He gets to the Kingston station, where Southern troops are stationed. Soldiers hop onto a train car and Johnnie fires up the engine – the Texas – but it isn’t attached to the cars. Johnnie keeps chasing the spies alone.
He notices a cannon mounted on a train car on a sideline and takes it along. The spies see him, but they don’t want to fight because they think they’re outnumbered. Johnnie fires the cannon twice; the first time the ball makes a little hop into his engine, but the second time (with the help of a whole can of gunpowder) it hits the back of the other train. The Northerners release that car to impede Johnnie, and he tries unsuccessfully to sideline it, but it eventually jumps the tracks after the spies toss baggage on the roadbed. They set fire to a second car and abandon it in a covered bridge, but Johnnie just pushes it out of his way.
Johnnie gets busy chopping wood for his engine. He’s so busy that he doesn’t notice the retreating Southern troops and the advancing Northern troops behind him. Now that he’s in enemy territory, the spies realize that he’s alone. He abandons the Texas and runs into the woods just as a downpour begins.
Lost, cold, and hungry, Johnnie climbs in the window of a house. It’s the Union headquarters. As he hides beneath the dining room table, the officers discuss plans for a surprise attack on the rebels the following morning. Then guards march Annabelle in, and they assign a bedroom to her. The officers retire for the night. Johnnie comes out, knocks the guards out, steals a uniform, and rescues Annabelle. She tells him he’s brave, and they spend the night sitting huddled together in the woods.
The next morning, they go to the rail yard, eager to get back and warn of the coming attack. Johnnie hides Annabelle in a sack and joins the queue of soldiers loading supplies into a car attached to the General. While he chats with an officer, Annabelle reaches out of the sack and pulls out a coupling pin, detaching most of the train from the engine. Johnnie tosses her onto the remaining car. Then he gets on his engine with a load of wood, which he uses to knock the Northerners out and off of the train (an unconscious officer remains). He starts his General and gets away. The Union army climbs abroad the Texas, and the chase beings.
With a good head start, Johnnie frees Annabelle from the baggage car and they stop for firewood. While most of the logs he tosses in don’t land on the car, she ties a rope across the tracks. He derides her efforts, but when the Texas runs into it, they are forced to stop.
Johnnie and Annabelle’s tussle continues: after he douses her with water while refilling the boiler, she stokes the fire with progressively smaller pieces of wood. He hand her a splinter, she throws it in, so he throttles her, then kisses her.
The Texas gains on them. Johnnie distracts the Northerners by uncoupling his baggage car, then he breaks a switch to block the track. The General arrives at the Rock River Bridge and Johnnie sets it on fire. After a Southern guard shoots at Johnnie, he trades the blue Union uniform he’s wearing for a gray one he found on the train. They hurry to the Confederate encampment while the Union officers try to fix the track. Johnnie alerts the Southern command, and Annabelle sees her father and runs to him. The troops quickly deploy to Rock River, and Johnnie follows them.
Meanwhile, a Union enlisted man whacks the switch with the blunt end of an ax and fixes it. The Texas arrives at the bridge. Their commander decides that the bridge isn’t burned enough to stop the train, and it forges ahead: right into the river. The commander gives a dispirited order to ford the river.
The Southern troops are in position on the bluffs above the river, and the battle begins. Johnnie fights to keep the blade in his sword hilt, then he goes to assist a cannon crew. One by one they are picked off by a sniper, until Johnnie raises his weapon, the blade flies off and impales the sniper. He fires the cannon, and though it misses its mark, it hits a small dam and floods some Union soldiers. The North retreats. Johnnie picks up the Confederate flag from its fallen bearer and waves it atop a hill.
The Southern troops return triumphant to camp. Johnnie visits his General, where he finds the groggy Southern officer. He arrests him and takes him before the commanding officer. He takes charge of the prisoner and orders Johnnie to take off his borrowed uniform, then he replaces it with that of a lieutenant. He finally enlists, giving his occupation as soldier. Annabelle is thrilled. They go sit on the General, but every time he tries to kiss her, a soldier passes by and he must salute. Eventually he figures out how to combine his two new roles of soldier and lover: he sits on her left, so he can kiss and salute at the same time. — Lisle Foote