Sam McCade4 books in series
Galactic Bounty Publisher's Summary
A traitor is on the loose. A treacherous navy captain plans to sell military secrets to the alien Il Ronn. The only man who can stop him is Sam McCade. Betrayed by his friends, stalked by his enemies, McCade is the only one standing between a terrifying alien threat - and the unimaginable devastation of the Terran Empire.