 Ron Glass as Derrial Book — a Shepherd (equivalent to a pastor). Although presented as a devout Christian, Book has profound, unexplained knowledge about criminal activities, police corruption, and military strategy, tactics, and weapons. In "Safe", he was shown to have sufficient status in the Alliance to receive emergency medical treatment from an Alliance ship, with no questions asked. He is also proficient in hand-to-hand combat and the use of firearms. While objecting to violence most of the time, on a rescue mission he joins the fight, stating that while the Bible is quite specific about killing, it is "somewhat fuzzier on the subject of kneecaps". Book is a moral guide for Mal and the rest of the crew, a voice of reason, conscience and spirituality. At the same time, he seems to get along well with the amoral mercenary Jayne, with the two spotting each other while working out using a bench press. His hidden backstory would have been gradually revealed, had the series continued, but was instead explored in the 2010 comic book The Shepherd's Tale.
