During the Cold War, the FBI arrests Rudolf Abel, a Soviet spy living in Brooklyn, New York, charging him with espionage. The American government enlists James B. Donovan, an insurance lawyer with a background in criminal justice, to provide Abel with a proper defense. Many see Abel's defense as a lost cause and even question Donovan's patriotism, but he's determined to give Abel a fair trial. Donovan insists on upholding the constitutional rights due to every individual, invoking the principles of justice and due process. He defends Abel all the way to the Supreme Court, emphasizing the importance of the rule of law, even as public and familial pressures mount against him due to his association with the Soviet spy.

Parallel to the trial, the U.S. military is running covert U-2 spy plane missions to gather intelligence on Soviet military capabilities. During one such mission, an American pilot, Francis Gary Powers, is shot down over Soviet airspace and captured. As tensions rise between the two superpowers, Donovan's role takes on new importance. The government tasks him with a critical clandestine mission: to negotiate a prisoner exchange in East Berlin at a time when the East-West Berlin divide is at its most volatile, with the construction of the Berlin Wall underway. Donovan must navigate a delicate diplomatic maze to secure Powers' release while also considering the fate of an American student caught by East German authorities.