The year is 1809, and the recruiting sergeants are hard at work, as the British army gathers strength for the next phase of the campaign against Bonaparte on the Spanish Peninsula. Captain Billy Pringle of the 106th Foot, however, has a somewhat more urgent reason to leave the country: having become embroiled in an ill-advised duel with a lieutenant in the 14th Light Dragoons, a posting to Spain would avoid any awkwardness for the regiment.

Along with his friend Lieutenant Williams - whose sister Kitty was the cause of the duel - and the doughty veteran Sergeant Dobson, Pringle takes on the task of training Spanish troops to stand alongside their British allies. But what seems at first like easy duty soon turns into a desperate fight for survival as they find themselves besieged in the strategic fortress of Cuidad Rodrigo.

For Bonaparte, taking the fortress will be the first step towards pushing the British back to the sea, and the task is entrusted to one of his most daring and successful generals, Marshal Ney. And Ney in his turn has found the perfect officer to lead the assault, a man not only desperate for advancement but also thirsting for revenge - a man whom Williams knows only too well.