David Balfour, the son of Alexander Balfour, is a young man when his father dies. After settling—he believes—all of his father's affairs, he wishes to go out into the world and make a successful life outside of his small village. He hopes that his relations at the house of Shaws can help him to make a start in the world. At the beginning of the novel, David is a naive young man with a strong sense of what he believes is right and wrong. Throughout the novel, that belief will be tested repeatedly. David finds himself aligning with an outlaw against his own family, a position that he often questions. He meets men of the church who threaten his life and others who are exemplars of Christian goodness and charity. David learns throughout the novel that he must judge each man individually and upon actions rather than words. David's understanding of what is right, just, and Christian evolves throughout the novel as he transforms from a naive boy to a man with experience of the world.
Alan Breck is a strong, clever man and a skilled fighter. His first interaction with David shows his calm demeanor under pressure. Alan's boat has capsized and he is the only survivor, but he is cool and collected, carefully assessing the men surrounding him. Although Alan is an outlaw, he is a respectable man with a firm sense of what he believes is just and moral—although this does not always align with what David believes. For example, Alan helps a guilty man escape from a murder charge because he believes it to be his Christian responsibility to help those "in difficulty." He plays cards and would engage a man in a swordfight simply because their clans have been fighting for decades. Alan's loyalty is based upon familial connections and personal relationships. He is loyal to his relatives, his clan, and the clans allied with his clan. He is loyal to David because David helped to save his life. Alan's particular brand of respectability challenges David to reconsider many of his principles.
Ebenezer Balfour is an angry old man who jealously protects what he owns, even if he does not really own it. Ebenezer is willing to provoke David's accidental death, paying Captain Hoseason to kidnap David, sell him into slavery, or even pay a highlander to keep him imprisoned for life. Ebenezer stops short of paying someone to actually murder his nephew, but as several of his plans are likely to have resulted in David's death, this is a subtle differentiation. He thinks up and executes a range of nefarious plots and only stops when he is caught admitting to one of them while a lawyer is present. Mr. Rankeillor explains that Ebenezer was not always this way, but that he was once a "fine and gallant" man. He never recovered from the jealousy he felt when his brother won the woman he loved. Even though he received the estate, it was not enough to keep him from becoming a bitter, spiteful old man.
Captain Hoseason is a brash, mean, selfish man who prioritizes profit and the success of his trading venture above the quality of life—and even above the very lives—of the men on his ship. Captain Hoseason is willing to kidnap David and sell him into slavery for the profit it will turn. He keeps Mr. Shuan on the ship despite his cruelty and abuse of the cabin boy Ransome because Mr. Shuan is an excellent navigator. Captain Hoseason cares more about the lost ship than for the lost men because losing the ship will be financial ruin for him.
Mr. Rankeillor is a good, just man whose reputation as such is known widely. Simply the mention of his name as a supporter or a lawyer can serve as some proof of the honesty of the person invoking it, as David does when asking the girl in the pub for help. Mr. Rankeillor, moreover, is an intelligent and inquisitive man. When he relates the story of what has happened while David was on his adventure, he reveals that he had come to support David before ever meeting him. Through his investigations into David's disappearance, initiated by the arrival of Mr. Campbell, Mr. Rankeillor discovered that something inappropriate had occurred. However, Mr. Rankeillor sometimes prioritizes what he believes is right above what is truly legal. In listening to David's story, he insists that David use fake names for anyone who might have broken the law, even though he implies that he knows their identities. He "forgets" his glasses so that he will not be able to testify to Alan's identity when they go to the house of Shaws together. Mr. Rankeillor does what he believes to be right, even when it is not quite legal.