Simon is a talented illustrator living a mundane life in 1970s New York City. Lacking strong family ties and feeling disconnected from modern society, he readily accepts an offer to join a top-secret government experiment. His artistic ability to focus on visual details, combined with his natural inquisitiveness, makes him highly receptive to the self-hypnosis techniques required for time travel.

Katherine is an antique store owner who recently inherited the business after the deaths of her foster parents. She possesses an incomplete, partially burned letter from 1882 connected to a family mystery. Her curiosity matches Simon's, and she actively supports his investigation into her family's past by helping him study historical materials.

Maj. Ruben Prien is an Army officer acting as the primary recruiter for the secret time travel project. Formerly a football player, his short, bald appearance and friendly demeanor conceal a commanding military presence. He firmly believes in the necessity of the government's work and displays an intense dedication to military objectives.

Dr. E. E. Danziger is a lanky physicist in his mid-sixties who founded the time travel project. While he is deeply motivated by scientific discovery, he possesses a strict moral compass and worries constantly about the ethical implications of altering history. He serves as the primary voice of caution against government overreach within the project.

Colonel Esterhazy is a tense, bright-eyed military official who helps direct the government's time travel initiatives. He prioritizes national interests and strategic advantages over scientific caution. His willingness to risk unintended historical consequences places him in direct opposition to the project's scientific founders.

Julia Charbonneau is an elegant young woman who assists her aunt in running a boarding house in 1882 New York. She is highly intelligent and quickly notices inconsistencies in Simon's behavior, making her suspicious of his origins. Facing limited economic opportunities, she approaches her social options with a practical mindset.

Jake Pickering is a large, intimidating city clerk residing at the Gramercy Park boarding house. He harbors a volatile temper and an intense obsession with acquiring wealth, leading him to orchestrate an elaborate blackmail scheme. He reacts with immediate hostility and physical intimidation toward anyone he views as a threat.

Andrew Carmody is a wealthy 1882 political figure tied to the corrupt Tweed Ring. He initially appears as a victim of extortion, though his involvement in embezzling public funds reveals a darker nature. His actions surrounding the blackmail exchange drive the central mystery of the story.

Dr. Oscar Rossoff is a psychologist from Johns Hopkins who assesses candidates for the time travel project. He evaluates participants' mental resilience and utilizes hypnosis to help them temporarily disconnect from the present day. He maintains a genuine enthusiasm for the scientific possibilities of the experiment.

Aunt Ada operates a boarding house at 19 Gramercy Park in 1882. She curates a warm, comfortable environment filled with parlor games and shared meals, creating a tight-knit community for her residents.

Ira Carmody is Katherine's deceased adoptive father. He preserved the strange history of his father's suicide and the cryptic blue letter that sparks the initial investigation into the events of 1882.

Martin Lastvogel is a historian tasked with educating time travel candidates on 1880s culture. He teaches Simon how to authentically dress, eat, and behave so he can blend into 19th-century New York without drawing attention.

Felix Grier is a friendly resident of the 1882 Gramercy Park boarding house. He shares his enthusiasm for the growing art of photography by lending Simon his camera during his stay.

Byron Keats Doverman is a resident of Aunt Ada's 1882 Gramercy Park boarding house. He contributes to the lively social atmosphere that deeply appeals to Simon.

Maud Torrence is another resident of the Gramercy Park boarding house. She forms part of the tight-knit community that makes Simon feel a profound sense of belonging in 1882.