In 1799 Richard Sharpe contemplates deserting from the British army in India but not out of cowardice. Private Sharpe only wants to better his life somehow with Mary Bickerstaff who is his love interest. However, Sergeant Obadiah Hakeswill sets up Sharpe for a severe flogging by goading him into a fight witnessed by an officer and an ensign. While receiving his flogging that would have likely killed him, General Harris sends for Sharpe.

Harris offers Sharpe a promotion to sergeant if he joins Lieutenant Lawford in a plan to rescue Colonel McCandless, who has been captured by the enemy and is imprisoned in the city of Seringapatam, capital of the Mysore Kingdom. Sharpe agrees and leaves with Lawford the next morning. While preparing to move into enemy territory disguised as deserters, Mary joins the two men.

The cavalry of Tippoo Sultan who is the king of Mysore, captures Sharpe, Lawford, and Mary. The men must agree to joining with the Tippoo's forces and Mary must work in the house of General Appah Rao. Tippoo allows Sharpe and Lawford to serve under Colonel Gudin of the French army who serves as a military advisor to the king. The British army arrives and begins preparations to breach the two walls surrounding the city. Unknown to the British command, Tippoo has been building a huge black-powder mine with the intention of destroying most of the invading army by means of a single massive blast between the walls. McCandless knows of this plan from Rao, who had warned of the mine and its location on the west walls of the city before McCandless was captured. McCandless manages to tell Sharpe about the mine in the hope that Sharpe can deliver the news to the British command.

Sharpe's only chance to deliver the news comes when Gudin orders him to ride a horse toward a fight in a wooded area outside the city and try to confuse the British. Unfortunately, Sharpe finds Hakeswill and they engage in a time-wasting fight. Hakeswill and other British soldiers are captured, and Sharpe's chance slips away.

Hakeswill reveals Sharpe's and Lawford's true identies, and Tippoo throws them in the dungeon with McCandless. Hakeswill is held in the dungeon as well, the Tippoo having spared his life for betraying Sharpe and Lawford. A large tiger is released when the two guards leave for the night or for other reasons. Meanwhile, Mary has agreed to marry one of Rao's relatives and is given a loaded pistol for killing herself if she must during the upcoming battle. She instead throws the pistol to Sharpe so he can kill the tiger and escape the dungeon. He does this and sets off the black-powder mine before it can do its damage to the British army. The British take the city, Sharpe kills Tippoo, and the British army promotes Sharpe to sergeant, but Hakeswill still lives even though Sharpe threw him to six chained tigers. Sharpe sees the skin of the tiger that he had shot draped over Tippoo's coffin, which ends the story and gives meaning to the title.