The Icarus Hunt — Timothy Zahn

Jordan McKell is a renegade star-freighter pilot struggling to survive in a galaxy where trade is monopolized by the oppressive Patth. But when he takes a job flying a broken-down antique ship and its "special cargo" to Earth, neither Jordan nor his mechanic-partner Ixil (an alien being with two ferret like "outhunters" linked to his neural system) has any idea of the stakes involved. Soon Jordan and Ixil find themselves lumbering through space on the Icarus with a ragtag crew, an unknown saboteur, and a large sealed container the Patth will do anything to intercept. It's not long before Jordan suspects he and Ixil are in the middle of a vast conspiracy that could change the course of human history. Unfortunately, he's right.