In the year 1880, Thomas Edison (Benedict Cumberbatch), an inventor facing financial strains in New Jersey, makes a groundbreaking revelation with the introduction of his electric light bulb. His ambitious plan aims to energize American neighborhoods through the use of Direct Current (DC) technology, which—though cleaner and more affordable than traditional gas lighting—faces significant limitations in terms of range and costly wiring infrastructure. Edison’s immediate objective is to electrify Manhattan’s 1st district, necessitating two buildings to accommodate his dynamos.

Edison makes a significant journey to the White House to showcase his invention, the Phonograph, to the US President. This pivotal meeting is further graced by the presence of JP Morgan, a prominent financier who frequently backs Edison’s projects, as well as Samuel Insull, Edison’s dedicated private secretary. During this encounter, JP Morgan proposes a partnership involving $150,000, but Edison resolutely declines, firmly opposing the idea of utilizing his inventions for deadly purposes.

In spite of his refusal for partnership, JP Morgan later provides funding to bring Edison’s electrifying vision to fruition in Manhattan. On September 4, 1882, the New York Stock Exchange (NYSE) is illuminated under Edison’s DC system, marking a significant milestone in his venture.

Meanwhile, George Westinghouse (Michael Shannon), a successful businessman and inventor from Pittsburgh, intrigued by Edison’s achievements, extends an invitation for dinner. However, Edison’s arrogance leads him to snub Westinghouse’s invitation, choosing to bypass Pittsburgh without a second thought, despite Westinghouse and his wife waiting eagerly at the station. In response to this slight, Westinghouse embarks on a quest to establish the superiority of Alternating Current (AC) technology, which boasts the ability to transmit power over vast distances at a fraction of the cost.

As the rivalry intensifies, both Edison and Westinghouse engage in a fierce campaign to secure the adoption of their respective electrical systems across American cities. It becomes increasingly clear that Edison’s DC current—which demands a staggering 100,000 feet of copper wiring for every 100 customers—is economically unsustainable. In contrast, Westinghouse’s AC technology can efficiently supply power across thousands of miles with a single generator, representing a staggering 75% increase in efficiency.

In March 1886, Westinghouse achieves a notable victory with a successful AC demonstration in Great Barrington. At the same time, Nikola Tesla (Nicholas Hoult) arrives in the United States and joins Edison’s team. Tesla, however, grows increasingly disappointed by Edison’s reluctance to adopt his revolutionary ideas regarding the efficiency of AC technology. Tensions mount as Tesla believes Edison has reneged on a financial promise, leading him to leave the company after his contributions are dismissed as mere jest.

Edison grows protective of his patents, launching legal action against Westinghouse for utilizing his lightbulb designs without permission. This legal confrontation extends to Edison’s quest to protect his intellectual property, including a specific lawsuit over corkscrew designs on the bulbs. Despite the onslaught, Westinghouse innovatively develops a twist-and-lock fitting to circumvent Edison’s claims.

In a desperate attempt to maintain his reputation, Edison publicly decries AC as dangerous, igniting a publicity battle, while Westinghouse combats Edison’s allegations with undeniable technological evidence. The personal toll weighs heavily on both men; Edison’s wife, Mary Stilwell Edison (Tuppence Middleton), passes away, while Westinghouse suffers the loss of his friend Franklin Pope (Stanley Townsend) from an electrical accident. With their personal and financial stakes rising, both men find themselves at crossroads.

As Edison resorts to commercializing his Phonograph to generate much-needed income, he engages in a seamless campaign to associate AC with danger, even working clandestinely with the creators of the electric chair—a stark contradiction to his earlier principles against creating instruments of death.

The turning point comes with the tragic electrocution of William Kemmler ([Conor MacNeill]) who becomes the first person to die by electric chair, an event that sparks public outrage and sees Edison testifying in favor of AC’s supposed humaneness. The media turns against Edison, highlighting his involvement in the cruel execution, leading to public vilification.

In a twist of fate, Tesla seeks a new beginning and teams up with Westinghouse to design a functional AC motor. Despite having an incredible idea, financial constraints mount for Tesla as tensions with his investors escalate, ultimately resulting in his dismissal from his own company.

As Edison’s company merges into the larger General Electric under the influence of Morgan, tensions heighten as both Edison and Westinghouse present bids to illuminate the 1893 World’s Columbian Exposition in Chicago. The fair becomes the battleground for their competing technologies, with Insull representing Edison and Westinghouse presenting his own case. Ultimately, the radiant success of the fair underscores Westinghouse’s triumph.

Within this chaotic landscape, Edison reflects on his legacy, suggesting that his potential next invention—the motion picture—might overshadow his name in the annals of history.

Tesla and Westinghouse embark on groundbreaking achievements, harnessing the power of Niagara Falls to revolutionize electricity distribution. Tragically, Tesla passes away alone and impoverished in a New York hotel room, unable to reap the rewards of his innovations. In 1911, Westinghouse receives the prestigious Edison Medal for his contributions to electrical engineering, cementing his place in history alongside the name of Edison. Ultimately, when Edison dies, the nation pays tribute by dimming its lights for one minute in honor of his incredible journey and legacy in the world of invention.