Sten Adventures Book 5: Revenge of the Damned
Allan Cole
 Sten and Alex are now POWs in a Tahn prison camp. They were taken captive during the last story (Fleet of the Damned) when their ship was rendered hors de combat. The first half of the book covers their time in the prison camp (from which they could easily escape if their duty did not prevent them) and their eventual escape from said camp. The second half involves being sent back to the same Tahn world by the Eternal Emperor to help topple the Tahn regime and end the Tahn War. They are successful in all accounts, but afterwards an internal assassination plot succeeds in killing the Eternal Emperor. As the story ends, however, there is evidence that he will be back. (Well, that's why he's called the "Eternal" Emperor- but that's a story for the next book.)