Walter Hartright is the first narrator in this novel and the closest thing it has to a central protagonist, as he compiles the various narratives and takes the lead in the investigation around which the novel is structured. This also makes him, to some degree, the author of the text. He is, therefore, one of the most active characters in the novel and the hero against whom the antagonists (Sir Percival and Fosco) work.

Walter is a drawing master who begins the novel short of money and looking for work. His friend Pesca, indebted to Walter for saving him from drowning, recommends him for a well-paid role teaching two young women at a country house in Cumberland, Laura and Marian. Walter falls in love with Laura, and all his actions from this point on are driven by his devotion to her. He is in this a typical romantic hero, and he is rewarded with a happily-ever-after ending, marrying despite the barriers of social status that appeared insurmountable when they first met.

Laura Fairlie is a wealthy young woman who will inherit a fortune when she turns 21 at her next birthday. She is beautiful and beloved by her half-sister, Marian Halcombe, with whom she lives.