Paul is a 26-year-old law prodigy who recently graduated from Columbia and secured a partnership at a New York firm. Hailing from a religious farming family in Nashville, he is highly sensitive to class differences and eager to prove himself in high society. He possesses an analytical mind and relies on linear narratives to organize vast amounts of legal minutiae.

Edison is the famed inventor of the direct current (D/C) lightbulb and a towering public figure. He operates an industrial laboratory in New Jersey, utilizing teams of engineers to rapidly test and refine ideas. Deeply protective of his public image, he views the rise of alternating current as a direct threat to his empire and legacy.

Westinghouse is the imposing, bearlike head of the Westinghouse Electric Company. He champions alternating current (A/C) technology, which promises to power entire cities from a great distance. As a businessman, he is bold, confident, and frequently dismissive of Edison's legal threats, preferring to focus on the mechanics of his products.

Tesla is an eccentric, brilliant Serbian engineer who previously worked in Edison's laboratory. He holds the key to practical alternating current technology but lacks interest in the commercialization of his ideas. He requires specific mathematical dimensions for his food, detests certain textures, and prefers the isolation of his pristine laboratory over public interaction.

Agnes is a famous, talented opera singer who gained widespread popularity performing male leads on the London stage. She moves comfortably through New York high society and understands the unspoken rules of power and reputation. Beneath her polished celebrity exterior, she is observant, protective of her independence, and deeply pragmatic.

Fannie is Agnes's protective mother and manager. She handles the business aspects of her daughter's career and actively seeks to secure Agnes's position in high society. She is shrewd, practical, and highly cautious about whom they trust with their legal affairs.

Bell is the immensely wealthy inventor of the telephone. Having successfully defended his patent against Edison and others, he retired to an enormous, rustic estate in Canada to focus on personal tinkering. He views the constant legal battles of the American patent system with disdain.

Morgan is a financial titan who holds immense power over the American economy. He owns sixty percent of Edison's stock and holds shares in dozens of companies on the New York Stock Exchange. He views business logically and unsentimentally, preferring stability and profit over personal rivalries.

Brown is a journalist and failed inventor who orchestrates a public smear campaign against Westinghouse's technology. He travels the East Coast conducting public demonstrations where he uses electricity to kill animals, aiming to associate alternating current strictly with death in the public consciousness.

Serrell is an experienced patent lawyer representing Nikola Tesla. He previously represented Edison's early patents before being dropped for a larger firm. He operates with a calm, moderate demeanor that masks a sharp, calculating legal mind capable of exploiting the inexperience of younger attorneys.

Marguerite is the gracious wife of George Westinghouse. She provides a warm, stabilizing presence in his life and frequently hosts business associates at their estate. She takes an active interest in Paul's personal life, attempting to play matchmaker during dinner parties.

Erastus is Paul's father, a devoutly religious pacifist who founded Fisk College in Nashville for former slaves. He views the decadence of New York City with skepticism and frequently reminds Paul to value personal integrity over wealth or fame.

Batchelor is Edison's longtime right-hand man and enforcer. He handles the practical, often unpleasant tasks required to maintain Edison's empire and tracks rival inventors across the city.

Fessenden is a bitter former engineer from Edison's laboratory. Angry over lost stock values, he accepts a lucrative offer to work for Westinghouse in exchange for sharing inside knowledge about Edison's factory-like invention process.

Carter is a senior partner at the firm Carter, Hughes and Cravath. He expects complete transparency from his junior partners and steps in to take control when Paul makes significant contractual errors.

Foster is the owner of a Midwest singing tour. After Agnes leaves his company due to his attempts to skim her pay and control her travel arrangements, he threatens her with a scandalous lawsuit to force her return.

Mabel is the wife of Alexander Graham Bell. She is completely exhausted by the constant legal battles surrounding her husband's inventions and refuses to tolerate any discussion of Thomas Edison in her home.

Ruth is Paul's mother. She shares her husband's unpretentious lifestyle and values, providing a calm, steady environment for her family and their guests.

Hughes is the other younger partner at Paul's law firm. He frequently checks in on the Westinghouse case and steps in alongside Carter to manage the fallout from Paul's legal missteps.

Coffin is the president of the Thomson-Houston Electric Company in Massachusetts. He enters the story as a subcontractor manufacturing generators for Westinghouse's expanding network.

Kemmler is a convicted murderer who becomes the first person subjected to execution via the electric chair, a process pushed by Edison's allies to demonstrate the dangers of alternating current.