Dragon and Thief

Dragon and Thief is the first of six novels Timothy Zahn wrote about a juvenile thief and the alien warrior who becomes his passenger, published in 2003. Jack Morgan has been raised by his uncle Virgil as a professional con artist, and when the story opens he is alone aboard the ship Virgil left him, with an artificial intelligence that imitates the dead man's advice and seldom lets him forget it.

Draycos belongs to a species that must take shelter in a humanoid host for part of every day, showing on his carrier's skin as a tattooed outline, and whose fleet has been destroyed by an enemy using a weapon nobody survives. The partnership is practical before it is anything else: Jack flies, Draycos fights, and together they work on the corporation that framed Jack for theft and then for murder.

The story runs at the speed of a chase, with one escape arranged on top of another, and the pairing gives the book its shape. Jack is a liar by training trying to become something else, while Draycos is a soldier with a strict code and very little interest in the boy's better instincts. The series was written for younger readers, and the two of them carry it between them across five more books.