Frederick Pryor, second from left, with his parents and twin brother on Feb. 11, 1962, a day after being released from an East German prison, where he was held on spying charges. (Matty Zimmerman/AP)

One of the most dramatic moments of the Cold War occurred Feb. 10, 1962, on a bridge connecting the then-divided states of East Germany and West Germany, when two high-profile prisoners — American pilot Francis Gary Powers and a convicted Soviet spy known as Rudolf Abel — were exchanged.

Delegations from the United States and Soviet Union stepped onto the Glienicke Bridge, between West Berlin and Potsdam, East Germany, in a tense scene portrayed in the 2015 Steven Spielberg film “Bridge of Spies.”

The two groups stood on opposite sides of a white marker in the middle of the bridge for 20 minutes, waiting for word that another American had been released from an East German prison, almost 20 miles away.

That prisoner was Frederic L. Pryor, a 28-year-old graduate student who had been detained in East Berlin for nearly six months. Dr. Pryor, who was denounced as a spy by his captors but never charged with a crime, died Sept. 2 at his home in Newtown Square, Pa. He was 86.

His family announced his death with notices in newspapers in suburban Philadelphia and his hometown of Mansfield, Ohio. The cause of death was not specified.

In 1961, Dr. Pryor was completing his PhD dissertation in economics at Yale University. He had been in Berlin off and on for almost two years, conducting research on the trade policies of countries in the Communist bloc. He routinely drove his sports car into East Berlin to attend conferences and meet colleagues before being caught up in the hard political realities of the Cold War.

On Aug. 13, 1961, Communist authorities in East Germany barricaded their half of Berlin behind barbed wire and hastily built concrete walls — what instantly became known as the Berlin Wall. Less than two weeks later, on Aug. 25, Dr. Pryor drove to East Berlin on what he expected to be his farewell visit.

His plan that day was to listen to a speech by East German leader Walter Ulbricht; to deliver a copy of his dissertation to a professor who had helped with his research; and to meet the sister of a friend.

The friend’s sister was not at home. (Only later did Dr. Pryor learn that she had fled west.) When he returned to his car, it was surrounded by officers from Stasi, the East German secret police.

“The Stasi were staking out her apartment to catch anyone coming to get her stuff,” Dr. Pryor told a publication of Swarthmore College, where he was a longtime faculty member. “I didn’t even get into the apartment, but they arrested me.”

When they found a copy of Dr. Pryor’s dissertation — filled with statistics and other information about the Soviet bloc — they accused him of economic espionage. He was taken to a notorious prison, where he was questioned for up to 10 hours a day.

“They interrogated me every day for four and a half months,” he later said. “Good practice for your German, by the way.”

Dr. Pryor’s parents moved to Berlin to help secure his release. As the weeks turned to months, he had almost no contact with them or anyone on the outside. The letters and packages his parents sent to him never arrived.

The East Germans furnished a lawyer for Dr. Pryor, but “once you’re arrested, you’re always convicted,” he told the Philadelphia Inquirer in 2015. “I expected five or 10 years in prison. I made peace with that.”

Meanwhile, the U.S. government was seeking to negotiate the release of Powers, whose U-2 spy plane had been shot down over the Soviet Union in 1960. In exchange, the United States would turn over Abel — a British-born Soviet spy whose real name was William Fisher — who had been serving a prison sentence for espionage since 1957.

When Abel was convicted, his lawyer, James Donovan (played by Tom Hanks in “Bridge of Spies”), argued that he not be given the death penalty.

“It is possible that in the foreseeable future,” Donovan said, “an American of equivalent rank will be captured by the Soviet Union or an ally. At such time, an exchange of prisoners could be considered to be in the best interest of the United States.”

U.S. intelligence officials enlisted Donovan to arrange the release of Powers in exchange for Abel. Dr. Pryor unwittingly found himself a part of high-stakes Cold War negotiations — in part because of the presence of his parents in Berlin.

Under pressure from the Soviets, East German authorities reluctantly agreed to release him as part of the Powers-Abel prisoner exchange.

“The East Germans weren’t happy about releasing me,” Dr. Pryor told the Swarthmore publication. “When my lawyer drove me to Checkpoint Charlie” — the central crossing point between East and West Berlin — “they had us sit there for half an hour. The East Germans deliberately delayed the exchange of Powers and Abel, who were not supposed to be exchanged until after I was released.”

Powers, Abel and the two countries’ diplomatic parties were forced to stand in the cold on Glienicke Bridge until U.S. officials learned that Dr. Pryor had been freed and was reunited with his family. The call came at 8:52 a.m. on Feb. 10, 1962.

Dr. Pryor flew back to the United States on a commercial flight and within 48 hours was in Ann Arbor, Mich., where his parents were living at the time.

“I did not know about the Powers-Abel switch until I crossed the border,” he said at the time. “I’m a private citizen and I don’t particularly enjoy the attention given me. I’d like to resume a normal life.”

Frederic LeRoy Pryor was born April 23, 1933, in Owosso, Mich., and grew up in Mansfield. His father was the wealthy owner of a manufacturing company, his mother a homemaker.

Dr. Pryor graduated in 1955 from Oberlin College in Ohio, where he majored in chemistry. He received a master’s degree in economics from Yale in 1957, then spent a good deal of time in Europe studying for his doctorate. Yale conferred his PhD in 1962, shortly after his return from captivity in Berlin.

When he applied for jobs with the auto industry, he was turned down.

“They said, no, they didn’t want anyone with a prison record,” he recalled. “I said, ‘But it was the commies!’ They said, ‘Tough.’ ”

Instead, he turned to the academic world. He taught at the University of Michigan and worked in research at Yale before joining the faculty at Pennsylvania’s Swarthmore College in 1967. He published more than a dozen books and more than 100 scholarly papers, examining the economics of Eastern Europe, agriculture, income inequality and other subjects. He retired in 1998 but kept an office at Swarthmore for many years afterward.

After the fall of the Berlin Wall, Dr. Pryor returned to the former East Germany, where he had a warm reunion with the attorney assigned to his case.

His wife of 44 years, economist Zora Prochazka, died in 2008. Survivors include a son, Daniel Pryor, of Washington, and three grandchildren.

Powers died in a helicopter crash in 1977; Abel died in the Soviet Union in 1971. Dr. Pryor seldom spoke about his Berlin experiences to his family or colleagues and said he was not consulted by Spielberg, the director of the “Bridge of Spies,” before the film was released. He had to buy a ticket and see it in a theater, like everyone else.

“Almost everything the movie showed about me was fiction,” he told Britain’s Independent newspaper. He thought Will Rogers, the actor portraying him, looked “like a delinquent.”

Leaving the theater, Dr. Pryor recalled to the Swarthmore publication, “another person asked me what I thought of the film, and I said parts of it were inaccurate. . . . He asked how I knew that, and I said, ‘I’m Frederic Pryor.’ ”