Si's girlfriend who owns an antique store and introduces him to the mystery of a letter from the past, sparking the main conflict of the story.

A catalyst for Si's involvement in the time travel project, Rube is a charming and perceptive military man who supports the project's goals.

A doctor and psychologist involved in the time travel project, he initially helps Si use hypnosis to travel to the past.

The director of the time travel project, he is a brilliant physicist with a strong moral compass, who eventually voices concerns over the project's risks.

A military figure who is a secondary antagonist, Esterhazy is involved in the time travel project with motivations centered around power.

Si's primary love interest, Julia is a young woman working at her aunt's boarding house, characterized by her beauty, intelligence, and emotional depth.

The main antagonist, known for his intimidating presence and obsession with wealth and power, he poses a threat to Si through blackmail and rivalry.

Initially introduced through a mystery, Carmody becomes a significant figure as the narrative unfolds, tied to the central conflict through his past actions.

The group that includes Aunt Ada and others, providing Si with a sense of community and belonging during his time in 1882.