George Colwan, Laird of Dalcastle
A wealthy, gregarious, and liberal man, he serves in Parliament and is not particularly religious. He marries Rabina but is frustrated by her fanaticism and attempts to convert him. He has two sons by her but only acknowledges George, the firstborn. He makes Arabella Logan his mistress, and the two live as man and wife. He is heartbroken by the news of his son's death, and dies not long after.
Rabina Colwan, Lady of Dalcastle
A zealously strict religious woman, she is disgusted by her arranged marriage to the Laird of Dalcastle, and shuns his attentions. She initially attempts to convert him but eventually chooses seclusion. She bears two sons, but will not acknowledge the first. She gives all her love and imposes all her violent piety on Robert; it is hinted that he may be the son of the Reverend, whose counsel Rabina has long received. She is missing and found murdered, and it is assumed that Robert did this.
Reverend Robert Wringhim
A strict and zealous man, he is the spiritual adviser and friend of Rabina, and the putative father of Robert Wringhim Colwan. He preaches predestination and the infallibility of the elect. He travels a great deal but oversees Robert's development, encouraging him to be more steadfast in his faith and doctrine, and helping secure his release from prison. He becomes concerned by Robert's friendship with Gil-Martin.
George Colwan
The son of Rabina and the laird, George is friendly, handsome, and polished. His good fortune is darkened by the persecution he experiences at the hand of his brother, and he becomes afraid, nervous, and withdrawn. He is unpopular for a time when the town's sympathies extend toward Robert, but the awareness of Robert's dogging his steps seems to be a victory for him. On the eve of a vacation he has planned, Robert and Gil-Martin murder him (although it is suspected that Drummond did it).
Robert Wringhim Colwan
The son of Rabina and most likely the Reverend Wringhim, Robert is a dark, intense, fanatically religious young man who strives to wage war against God's enemies. He becomes one of the elect but often doubts the infallibility associated with such a state. He befriends Gil-Martin, a shape-shifting doppelganger, entranced by his intelligence, spiritual superiority, and flattery. At this friend's urging he begins to carry out persecutions and murders, including that of his brother. He inherits the lands of the laird, but his life becomes misery as he finds he cannot extricate himself from his friend's clutches; he descends into despair and loses his sanity and all sense of time. He flees his home for suspicions of having murdered his mother and a young lady, and spends the rest of his life also trying to escape Gil-Martin. This is impossible, though, and after laying out his account in a memoir, he hangs himself at the urging of Gil-Martin.
Miss Arabella Logan
The Laird's pretty, "jolly" mistress and adopted mother of George, Miss Logan tenaciously tries to probe the true cause of George's death, and works with Bell Calvert. She is a high-strung woman, prone to fainting, but nevertheless pursues her quest.
Adam Gordon
George Colwan's friend, to whom he confides his fears about Robert.
Thomas Drummond
One of George's friends. Drummond is accused of murdering George because, the night of his death, George was seen quarreling with him, and a man with his likeness was seen at the murder. Bell Calvert also tells Drummond’s story; he was seduced by her until he thought better of it and left. He flees the country from his murder charge and ends up serving in the German military.
Bell Calvert
A prostitute who is witness to the murder of George Colwan. She works with Arabella Logan to secure the indictment of Robert. She is described as elegant and proud but drawn, and her life was one of misery at the hands of men.
Bessy Gilbert
Miss Logan's maid who is summoned to testify in Bell's trial. Her testimony is not useful in convicting Bell, on account of its scrupulousness.
M'Gill
The young student whom Robert torments because he is jealous of the boy's superiority in their studies.
John Barnet
The Reverend's serving-man, whom both he and Robert dislike. He quits his post when the Reverend becomes angry at him for saying that he was Robert's true father. He intervenes to help Robert in a fight, but is not thanked for his trouble.
Gil-Martin
A mysterious creature that may be the devil, a person imbued with unknown qualities, or a figment of Robert's imagination. He can change his appearance to resemble that of others, and claims to understand their innermost thoughts as well. He seduces Robert with his intellect and charm, and encourages him to pursue his religious fanaticism to murder. Robert thinks he is Czar Peter of Russia, as he has no lodgings, an ambiguous background, and elegant deportment. He plagues Robert for the rest of his life, pursuing him and trying to convince him that he has his best interests in mind. He seems to languish, though, and becomes diminished in appearance if not in powers of persuasion. He convinces Robert to commit suicide and says he will do the same.
Mr. Blanchard
A worthy, pious religious man who lives near Robert when he is young. He tries to warn Robert about the extremity of his friend's ideas. Gil-Martin encourages Robert to murder him because he is an enemy of the faith, and they undertake this successfully even though Robert is wary.
Lawyer Linkum
The lawyer who reveals that Robert signed a document taking Mrs. Keeler's lands.
Samuel Scrape
Robert's new servant, whom he is told he hired during the six months that he does not remember. Scrape is pleasant to Robert, and even warns him in advance that an angry mob is seeking him for the deaths of his mother and lady. Samuel is witty, humble, and pleasant enough.
Linton
Robert's roommate for a time, who helps get him a job at the printing house.
Mr. Watson
Robert's boss at the printing house, who destroys copies of his manuscript for being evil.
The Editor
The Editor's narrative concerns the history of what he had learned about the events found in the manuscript. His curiosity regarding this story is piqued when he sees Hogg's letter, and undertakes a journey to discover more about what had happened. He confesses he does not know exactly what the manuscript is, and how much is truth or fiction.
James Hogg
The writer whose letter to Blackwood's about the digging up of the suicide prompted the Editor's visit to the site and discovery of the manuscript; he is the author himself, but the novel was published anonymously.
Mrs. Keeler
The old woman and neighbor of Robert, whose daughter he apparently seduces and whose land he apparently steals in order to secure the girl.
