NOTE: This spoiler was submitted by Jeremy

The film opens in 1954 at the start of a security hearing for renowned physicist J. Robert Oppenheimer (Cillian Murphy). It jumps between the following years as Admiral Lewis Strauss (Robert Downey Jr), accompanied by his Aide (Alden Ehrenreich), is acting against Oppenheimer during a Senate hearing due to believing he has ties to communism, as well as a personal grudge stemming from when the two met back in 1947. Strauss had tried to recruit Oppenheimer to a position at Princeton. Oppenheimer makes a condescending remark about Strauss’s background as a shoe salesman, and later, Strauss watches as Oppenheimer speaks to Albert Einstein (Tom Conti). When Strauss tries to greet Einstein, the man doesn’t acknowledge him, and Strauss is left to believe that Oppenheimer said something about him to Einstein.

Back in 1924, Oppenheimer begins as a physics student at Cambridge under Patrick Blackett (James D’Arcy). Oppenheimer wants to attend a lecture by Niels Bohr (Kenneth Branagh), but Blackett makes him stay behind and finish working on his project. Oppenheimer goes into the cabinet and injects an apple on Blackett’s desk with potassium cyanide, before sneaking off to Bohr’s lecture. The next day, Oppenheimer personally meets Bohr and stops him from eating the tainted apple. Bohr is impressed by Oppenheimer’s knowledge and research, and he encourages him to educate himself where he will feel less restrained.

Oppenheimer begins studying at the University of Gottingen, where he meets Isidor Rabi (David Krumholtz) and works toward his PhD. Along with Rabi, they meet theoretical physicist Werner Heisenberg (Matthias Schweighofer), whom Oppenheimer reveres as an influential figure in his work. He later begins teaching at Berkeley back in the States, where he is referred to as “Oppy” by his peers, including Nobel Prize winner Ernest Lawrence (Josh Hartnett). Oppenheimer begins his lectures with just one student, Giovanni Lomanitz (Josh Zuckerman), but later ends up having a much larger and fuller class.

Oppenheimer later attends a Communist Party gathering with his younger brother Frank (Dylan Arnold) and his girlfriend. There, Oppenheimer meets and befriends Haakon Chevalier (Jefferson Hall). He then meets Jean Tatlock (Florence Pugh), chatting with her before taking her to bed. After sex, Jean looks through the books on the shelf and takes one out in sanskrit, asking Oppenheimer to translate. It reads, “And now I am become death, the destroyer of worlds.”

Oppenheimer goes with Frank and Lawrence to a ranch in Los Alamos. Frank and his girlfriend have officially joined the Communist Party, which Oppenheimer discourages, despite his own left-leaning political views that earn him raised eyebrows. He posts support for the Spanish Revolution, which Lawrence questions. Oppenheimer also joins the Federation of Architects, Engineers, Chemists and Technicians (FAECT), which further fuel others’ concerns that Oppenheimer is a communist.

During an afternoon out with Jean, Oppenheimer sees one of his students, Luis Alvarez (Alex Wolff) reacting frantically because news has broken that the Germans have split the uranium nucleus by bombarding neutrons through nuclear fission. Later, during a party with the FAECT, Oppenheimer learns of Hitler invading Poland.

Oppenheimer later meets Katherine “Kitty” Puening (Emily Blunt), a member of the Communist Party who is already in a failing marriage. After she splits from her husband, Kitty begins a relationship with Oppenheimer, eventually marrying and getting pregnant by him. He goes to break things off with Jean, who is upset despite earlier trying to tell Oppenheimer that she did not want to continue the affair. Kitty gives birth to a son, Peter, and she becomes an alcoholic. The two leave Peter with Chevalier while they take a trip.

At the university, Oppenheimer is met by General Leslie Groves (Matt Damon) and Lt. Colonel Kenneth Nichols (Dane DeHaan) to recruit him to be the director of the Manhattan Project to develop an atomic bomb during World War II. Oppenheimer begins to recruit other scientists such as Richard Feynman (Jack Quaid), Kenneth Bainbridge (Josh Peck), Seth Neddermeyer (Devon Bostick), Lilli Hornig (Olivia Thirlby), as well as Lomanitz and Alvarez. They set up shop in Los Alamos where they construct a fake town near the testing site. Edward Teller (Benny Safdie) is brought in, and after he reviews the schematics and components of the bomb, Oppenheimer and the others realize with horror that in the wrong hands, a hydrogen bomb more powerful that the atomic bomb can be developed and possibly cause a chain reaction that will destroy the world. After some more research, the chances are reduced to “near zero”.

Another flashforward shows Oppenheimer forming a program for the hydrogen bomb with the Atomic Energy Commission. The men gather with their colleagues after the Soviet Union tests their atomic bomb. Strauss and Nichols, both staunch anti-communists, discuss the notion that there were several communists working on the Manhattan Project.

During the security hearing, Oppenheimer’s involvement with Chevalier is discussed due to him trying to get infromation on the project on behalf of the Russians, which was treasonous. Lomanitz was also drafted due to his involvement in left wing politics making him look like a risk. The matter is also complicated further during Oppenheimer’s time on the project when he meets Colonel Boris Pash (Casey Affleck), who is the project’s head of security and also personally goes after communists. An anti-communist lawyer, William Borden (David Dastmalchian), presents the members of the hearing with an indictment on Openheimer.

Oppenheimer’s relationship with Jean is also called into question, with flashbacks showing that he continued their affair. He admits to his adultery with Kitty present in the room, and she envisions Jean having sex with her husband in front of her. In 1949, Jean commits suicide via an overdose and drowning in the bathtub, although there is a quick glimpse of what appears to be a hand forcing her head into the water, suggesting Jean was possibly murdered and was set up to look like a suicide. Kitty finds Oppenheimer in the woods having a breakdown over the news, but she tells him to pull himself together.

Sometime during the project’s development, Bohr is brought to Los Alamos after being stuck in Europe due to nazi occupation. He contributes to the project’s work with Oppenheimer and Teller. Bohr tells Oppenheimer that he is giving mankind the power to destroy themselves.

After Hitler’s death, the team continues with the project since they know the Japanese are continuing their wartime efforts. The team carries out several bomb tests. After some time, they perfect their bomb and get ready to initiate what Oppenheimer calls the Trinity Test. Everyone gathers at a safe distance at night and prepare for the outcome. The bomb detonates and produces a powerful mushroom cloud and subsequent shockwave. Oppenheimer then repeats the phrase, “And now I am become death, the destroyer of worlds”. The team celebrates their success.

President Harry Truman (Gary Oldman) later drops atomic bombs on Hiroshima and Nagasaki, which begins to weigh on Oppenheimer’s conscience over the resulting casualties. He gives a speech to the team, who are all cheering him on, but he envisions the effect of the bomb incinerating everyone. Oppenheimer later meets Truman, who initially congratulates him on the bomb’s development, but when Oppenheimer says he has blood on his own hands, Truman sends him out and calls him a crybaby.

Years later around the time of the Senate hearing, Strauss tells his Aide that Frank was blacklisted from every university due to being a communist, Lomanitz ended up working on a railroad, and Chevalier went into exile. Oppenheimer had begun to try for an arms control program as opposed to one for the hydrogen bomb, but Truman rejected it. Strauss had also informed Oppenheimer that one of the members of the Manhattan Project, Klaus Fuchs (Christopher Denham), was a spy for the Soviets and fed them information on their research and development. Oppenheimer’s advocacy for stopping development of further nuclear weapons is looked down upon due to the Cold War. Strauss is also seen working with Borden and Nichols to try and get more dirt on Oppenheimer.

Throughout the time of the security hearing, Kitty becomes angry at Oppenheimer for seemingly trying to self-sabotage himself so that he may look like a martyr due to his guilt over his creation. Oppenheimer is interrogated by Roger Robb (Jason Clarke) as others like Teller, Rabi, Groves, and Pash give testimonies about their time spent with the man. Robb demands to know where Oppenheimer’s views on nuclear weapons development changed, and he says it was when he realized that America would use whatever weapon that had to win at all costs. Because of Teller and Groves, Oppenheimer is ultimately deemed loyal to America, but he has his security clearance revoked and loses his political influence.

Strauss vies for a position on the Senate, but former technician David Hill (Rami Malek) gives a testimony against Strauss due to his actions against Oppenheimer over personal grievances, including a moment during another hearing where Oppenheimer referred to Strauss as being “more useful than a sandwich”. Strauss loses his chance at the Senate, and the Aide turns on him after realizing his intentions. The Aide also lets him know that JFK was against Strauss’s actions.

We then see the conversation Oppenheimer has with Einstein before Strauss approaches them. One more flashforward in their discussion shows Oppenheimer in 1963 receiving the Enrico Fermi Award from President Lyndon B Johnson. They talk about the implications that their work in nuclear weapons may have started a chain reaction that has doomed the world. Oppenheimer then sees visions of nukes going off around the world, engulfing the planet in fire and ash.

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The film goes back and forth between various points in the life of J. Robert Oppenheimer, the father of the atomic bomb. While teaching at Berkeley, he is approached by General Leslie Groves to become the director of the Manhattan Project to develop a bomb during World War II. Their efforts prove successful during the Trinity Test, but after President Truman orders bombs dropped on Hiroshima and Nagasaki, Oppenheimer begins to feel a sense of guilt over the casualties in the bombings.

Oppenheimer becomes an advocate against further nuclear weapons developments, as his colleague Edward Teller has found a way to develop a hydrogen bomb more powerful than the atomic bomb, which can also possibly set off a chain reaction that would destroy the world. Oppenheimer is later involved in a security hearing due to his ties to communist circles, which included his wife Kitty as a former member. His affair with Jean Tatlock is also brought up. His security clearance ends up being revoked and he loses political influence. Meanwhile, Admiral Lewis Strauss works against Oppenheimer due to personal grudges against him, but a former technician testifying against Strauss costs him his chance at the Senate.

Oppenheimer is later given the Enrico Fermi Award near the end of his life, but the film ends with him fearing that his work in nuclear weapons may have doomed the world.