He serves the Tippoo Sultan of Serengapatam as a consultant, and is the liaison for foreign troops serving the sultan. When Sharpe and William Lawson arrive in Mysore pretending to be deserters, Gudin tells them he is never sure if deserters should be trusted. Sharpe responds that some had good reason for running and displays his recently flogged back. Gudin shudders, and calls the practice of flogging barbarism. He then called for the sultan's physician, Venkatesh, who treats Sharpe's back and greatly improvs the subsequent healing of the terrible wounds. Gudin was of the opinion that under the care of the army surgeon Sharpe, would have died within the week. Under Indian medicine, his healing is far more complete than a man left an army surgeon's mercies.
Gudin gives Sharpe his first opportunity to fire a rifle, one of the Sultan's own highly decorated weapons, with which he fires on British cavalry, wounding one, nearly a thousand feet away in order to maintain his cover.
Once Sergeant Hakeswill betrays Lawford and Sharpe to the Tippoo, it was Gudin who gentlemanly took Lawford's confession as to his real rank as well as Sharpe's, and promised he would plead for their lives. Disarmed and taken into custody, Sharpe says, "It was an honor to serve with you, sir. I mean that. I wish we had more like you in our army." (Sharpe's Tiger). Gudin offers him a chance to actually desert, but Sharpe refuses, as Gudin had expected he would.
Once Sharpe and Lawford escape from the dungeons during the British attack on Serengapatam, Gudin tries to disarm them, when Sharpe refuses to yield, Gudin regretfully takes aim with his pistol, while Sharpe fires a musket from the hip, wounding Gudin high in the right shoulder, breaking it. Sharpe apologized. Gudin appears close to tears, not due to the pain, but because he had failed in his duty. When he asks Lawford what would happen to him, he was told he will be treated well, perhaps be sent back to France. He allows that he will like that, then offers Lawson advice, telling him to look after Sharpe who was a good man, and on such men are armies built.
Gudin does not reappear until 1813, in the short story, Sharpe's Christmas, when he was described as grey haired and tired. He had returned to France after a year as a a prisoner of the British, after which he had been exchanged. He had received no promotion in 13 years, and was considered unlucky. From about 1810 until the end of 1813 he commanded the 300 man garrison at the fort at Ochagavia which was ordered abandoned at year's end. An additional 700 refugee troops from the defeat at Vitoria were under his command at the time; a handful of dragoons and men of the 75th Infantry under Colonel Caillou.
When faced with a British force, he responded to their white flag to parley, Caillou drew a pistol and told the British to go away, there would be no parley. When the young British ensign moved to curb his horse, Caillou shot him. Gudin then summarily shot Caillou, and told d'Alembord that to his shame he commanded.
When he finally met the British commander, he embraced Sharpe and kissed him on both cheeks in the French manner. He told Sharpe he was very proud of him, and that he had not changed at all - a soldier through and through. He surrendered his forces to Sharpe, and told of his poor career since India. Sharpe manufactured a false battle and allowed Gudin and 100 men of his garrison and their women and children 'to escape' back into France.
Instead of a young Sharpe, the television version of the story was of a much older Sharpe, although Gudin still made an appearance, his influence was greatly reduced, and he was in fact killed by story's end.