Follows 'Sharpe's Tiger' and 'Sharpe's Triumph'.
It is December, 1803, and Richard Sharpe is now an officer in Sir Arthur Wellesley's army that is seeking to end the Mahratta War. Sharpe, just risen from the ranks, discovers that his fellow-officers are not welcoming. Unsure of his authority and uncomfortable in the mess, he is failing, and his failure seems assured when he is relegated to a tedious job in the baggage train.
There Sharpe discovers a treason has been conjured up by his oldest and worst enemy, Sergeant Obadiah Hakeswill, but in uncovering this Sharpe finds himself alone and under dreadful threat. He falls back on his fighting ability to regain his confidence and his treasure, the jewels of the Tippoo Sultan, which have been stolen from him.
The search for revenge on the men who robbed him takes him to Gawilghur, the fortress in the sky, the last refuge of a desperate enemy. Gawilghur has never fallen to assault, and bolstering its defences is the renegade Englishman, William Dodd, who escaped from Sharpe in 'Sharpe's Triumph'. The fortress, poised high above the Deccan Plain, seems impregnable, and contains a trap for its attacker. Dodd is confident that no redcoat can reach him, but Sharpe is desperate and so he joins Wellesley's troops as they surge across the neck of land that leads to the breaches. There, in the horror of Gawilghur's ravine, dominated by walls and guns, he will fight as he has never fought before.
'Sharpe's Fortress' completes the story of Sharpe in India, following Ensign Sharpe from the heat-baked battle of Argaum to the carnage at Gawilghur. It leaves Richard Sharpe poised to return to Europe and to new, even more lethal, enemies.