A young private, Penton Gray, known as Pen, is injured during an engagement in the Peninsular War. When he comes to he finds that the boy bugler, Punch, from his regiment, is lying injured close by. The British troops are near, but the area where the boys are is occupied by the French, who are the enemy. The boys need to recover from their wounds, and then to get back to their regiment. They have numerous adventures, and meet several people who help them, including the deposed Spanish King.