Sharpe's Devil: Napoleon and South America, 1820-1821 (The Sharpe Series, Book 21) by Bernard Cornwell
Taking Richard Sharpe to St Helena and Chile, this is an adventure story in the classic tradition. Five years after the Battle of Waterloo, Sharpe,s peaceful retirement in Normandy is shattered. An old friend, Don Blas Vivar, is missing in Chile, reported dead at rebel hands - a report his wife refuses to believe. She appeals to Sharpe to find out the truth. So it is that reluctant Sharpe, along with Patrick Harper, find themselves bound for Chile via St. Helena, where they have a fateful meeting with the fallen Emperor Napoleon. Convinced that they are on their way to collect a corpse, neither man can imagine that dangers that await them in Chile...Soldier, hero, rogue - Sharpe is the man you always want on your side. Born in poverty, he joined the army to escape jail and climbed the ranks by sheer brutal courage. He knows no other family than the regiment of the 95th Rifles whose green jacket he proudly wears.