Franklin Blake is the driving editorial force behind the narrative of The Moonstone. He is intelligent and well traveled. He is trusted and liked by everyone in the Verinder household. Rachel falls in love with him, and he with her. However, his debts and his seemingly harsh treatment of Rosanna Spearman cast doubt on his character. He does his best to separate the events of the theft of the Moonstone into the subjective and objective, hoping to unravel the mystery of the Diamond. When his attempts to separate fact from emotion don't yield results, he seeks help and guidance from others with more knowledge, such as Sergeant Cuff, Mr. Bruff, and Ezra Jennings. He tenaciously pursues the identity of the true thief, even after his own name is cleared.
Rachel Verinder is a loyal and passionate young woman. She falls in love with Franklin Blake but sees him take the Moonstone from her room on the night of her birthday. When Blake seems to pretend he doesn't know what happened to the Diamond and leads the investigation, she is furious with him. However, she does not tell the police of his involvement. She refuses to speak to anyone about the night of the theft, even though she herself falls under suspicion. She eventually accepts Godfrey Ablewhite's offer of marriage, but discovers he's as duplicitous as she believes Blake to be. Rachel breaks off the engagement, once again keeping the reason to herself. With Blake, she is torn between trusting the evidence of her own eyes or believing what her emotions tell her. Eventually, she chooses to believe him and helps to clear his name.
Godfrey Ablewhite appears to be an upstanding Christian man, interested in charity work and helping others. In reality, he is a man who lies, cheats, and steals, merely pretending a piety he does not feel. His interest in Rachel is only for her fortune, and his interest in the Moonstone is only in the amount of money he can get for it. He steals the Moonstone to pay off his debts, but runs afoul of the Indians who have been following the Diamond in the hopes of retrieving it and returning it to India. He ends up dead, his double life revealed for all to see.
Gabriel Betteredge is a loyal and trusted member of the Verinder household. He is a kind-hearted man, especially compassionate toward Rosanna Spearman. He fancies himself an amateur detective and spends time helping Sergeant Cuff with the mystery of the lost Diamond. He refuses to believe Rachel could be responsible for the theft and gets quite angry with Cuff, even as he admires his intellectual prowess.
Miss Clack is a woman more interested in appearing to be pious than actually being a good Christian. She dislikes Rachel and greatly admires Godfrey Ablewhite. She is interested in converting Lady Verinder and Rachel to Christianity for hypocritical reasons. She believes Godfrey Ablewhite is completely innocent of the Moonstone theft, thinking Franklin Blake a more suspicious character. She is pleased when Ablewhite and Rachel's engagement ends and easily accepts his version of events.
Ezra Jennings is a contradiction in appearance and temperament. His face looks old but he moves like a young man, and his hair is both white and black. His striking appearance causes people to shun him. He's been falsely accused of a crime, but because of a terminal illness, he'll be dead before the gossip catches up to him. Jennings helps Franklin Blake because he believes him to be innocent based on information gleaned from Mr. Candy. It is his idea to re-create the night of the theft to see if Franklin Blake could have taken the Moonstone without remembering it while under the effects of laudanum. He himself is an opium addict because of his illness. Despite his strange appearance, he becomes a trusted friend to Blake and Rachel before his death.