Spain in 1810: Captain Anthony Trumbull is tasked with securing a huge cannon that the Spaniards left behind in retreat from Napoleon's troops. With the help of a British officer, he lifts the cannon out of a ravine and repairs it. Under great strain, they manage to get the heavy gun over 1000 kilometers in front of the walls of the city of Ávila and take it by storm after shooting a breach in the walls.