In 1918, Burt Berendsen (Christian Bale) was sent by his estranged wife's parents to fight in World War I. While stationed in France, Burt befriends African-American soldier Harold Woodman (John David Washington). Harold had refused to follow cowboy officers, who cared nothing for colored lives, and that's when Burt was assigned as his officer. Burt promised to treat Harold fairly and they and Milton (Chris Rock) ended up becoming lifelong friends. Bill Meekins was their General in charge and took good care of all his troops. After sustaining injuries in battle, Burt and Harold are nursed back to health by Valerie Bandenberg (Margot Robbie), an eccentric nurse who makes art out of shrapnel removed from the soldiers, whom they befriend as well.After the end of the war, the three live together in Amsterdam and become close friends. Valerie introduces Burt to Paul Canterbury & Henry Norcross who fits him with a glass eye. Paul and Henry are spies for MI6 and US Naval Intelligence respectively and use the glass eye business as cover to be in Europe. They agree to help Burt and Harold in exchange for a future undefined favor. Burt returns to New York City to be with his wife. Harold has fallen in love with Valerie and begun a tenuous romantic relationship with her. But Valerie abandons Harold when he talks about going back to New York to become a lawyer. Valerie says that she escaped her family and doesn't want to go back to where she came from. Harold really wants to help the war veterans who have no rights in USA, so he returns to New York.Fifteen years later in 1933, Burt has opened his medical practice catering to veterans of the war, and remains friends with Harold, who is now a lawyer. Burt has a glass eye and is constantly inventing new pain killers to help his patients to get through the pain of the injuries from the war. Burt is estranged from his wife Beatrice (Andrea Riseborough). Milton King is in touch with them as well. However, they have not heard from Valerie since they left Amsterdam. Harold asks Burt to perform an autopsy on Bill Meekins (Ed Begley Jr.) (a senator who served as the commander of their regiment during the war) at the behest of Meekins' daughter Elizabeth (Taylor Swift), who believes that he was murdered during his recent trip to Europe. Burt performs the autopsy with the help of medical examiner Irma St. Clair (Zoe Saldaña). The autopsy reveals a considerable amount of poison in Meekins' stomach; Burt and Irma theorize that this must have been his cause of death. Burt and Harold meet with Elizabeth to talk about the autopsy results, though she is suddenly killed when a hit-man pushes her into traffic. Elizabeth did not want to meet Burt and Harold just before her death and kept saying that Mr Voze, a friend of the family, asked her to be careful. The hit-man frames Burt and Harold for her death, and they flee as the police arrive.Burt and Harold attempt to find out who told Elizabeth to hire them in order to clear their names. Det. Lem Getwiller (Matthias Schoenaerts) & Det. Hiltz (Alessandro Nivola) are assigned to the Elizabeth case and track the duo to Beatrice's apartment. Harold says that he had a contract with Elizabeth as her lawyer, and they have the autopsy report on Bill Meekins to prove their innocence. Burt also proposed to get someone from the social register, like Mr Voze, to vouch for him. The hit-man continues to pursue Harold and Burt, but never kills them or attacks them.This leads them to wealthy textile heir, Tom Voze (Rami Malek), his patronizing wife Libby (Anya Taylor-Joy), and Tom's sister, Valerie (whose real surname is Voze). They learn that Valerie was the one who convinced Elizabeth to hire them, knowing that they were trustworthy. Valerie is under constant supervision by Tom and Libby, who claim that she suffers from a nerve disease and epilepsy. It is later revealed that they were poisoning Valerie to keep her compliant. Burt and Harold talk with Tom, who suggests they talk to General Gil Dillenbeck (Robert De Niro), a famous and decorated veteran who is friends with Meekins, to learn who accompanied Meekins on the trip (and might have poisoned him or be able to lead them to the person who did).While Burt attempts to contact the General, Irma visits him at his medical practice and reveals that she was attacked, and her wrist broken while trying to bring him the autopsy report and the attacker took the paper from her. After resetting her wrist, Burt and Irma share a kiss. Irma tells Lem and Hiltz how the autopsy results were stolen from her. The report said that Meekins had high dose of mercury and Luminol in his stomach, given to him in the last week of his life.Meanwhile, Harold and Valerie spend the day at her home, where they notice the hit-man, Tarim Milfax (Timothy Olyphant), has been watching the house. They follow him to a forced sterilization clinic owned by a mysterious organization known as the "Committee of the Five". After a fight with Milfax, Harold and Valerie reunite with Burt. Valerie takes them to the Waldorf Astoria New York, where they meet Paul Canterbury (Mike Myers) and Henry Norcross (Michael Shannon), Valerie's benefactors from Amsterdam who are secretly spies in the intelligence community. Paul and Henry explain that the Committee of the Five is a cabal in the US with ties to Germany planning to overthrow the American government and that Dillenbeck can help foil their plot.The trio meets with General Dillenbeck, who is offered a large sum of money from a man on behalf of an unnamed benefactor to deliver a speech advocating for veterans to forcibly remove U.S. President Franklin D. Roosevelt and install Dillenbeck as a puppet dictator instead. Dillenbeck says that Meekins had called him from Rome a few weeks back and has told him that he had seen something terrifying, which had disturbed him greatly. Dillenbeck is sure that this is why Meekins was killed on his way back to USA. The General agrees to help the trio foil the plot and agrees to speak at a veteran's reunion gala Burt and Harold are hosting in order to draw out whoever is behind the plot.At the gala, General Dillenbeck reads his speech instead of the one he was paid to read. Milfax tries to shoot him for doing so, but Harold and Valerie and then Burt manage to stop him in time. Milfax is arrested and the Committee of the Five is revealed to be four industry leaders, including Tom, who is fanatically obsessed with Benito Mussolini and Adolf Hitler, and intend to turn the United States into a fascist country.Tom and the other leaders are arrested by the police, but they do not stay in jail long, and slander General Dillenbeck in the press following their release. General Dillenbeck testifies about the incident to Congress and returns home to live out his life. Harold and Valerie leave the country since they cannot be together in the United States. Burt wishes them farewell, planning to reopen his medical practice and pursue a relationship with Irma.