BANGOR — When he was young, Richard Bissell III knew almost nothing about his late father’s work, and for very good reason.

Richard Bissell Jr. was one of the most influential spies in American history.

Among the earliest recruits to the CIA, Bissell worked for the spy agency in Washington D.C. during the Cold War years of the Truman, Eisenhower and Kennedy administrations. At his zenith, the Yale University-trained economist was an assistant to CIA Director Allen Dulles as deputy director for plans, the heart of the CIA.

Some of the agency’s most successful and most nefarious spy operations bear Bissell’s imprimatur. He plotted with gangsters to assassinate Cuban leader Fidel Castro, toppled Latin American governments, directed U-2 spy plane flights over the Soviet Union, and, his son believes, helped turn a desolate expanse of Nevada into Area 51.

Books describe Bissell’s father as brilliant, adventurous, energetic, tenacious and gutsy, but also petulant, ruthless, deceitful and contemptuous.

For most of his life, and in the 19 years since his father died, the 71-year-old retired Eastern Maine Medical Center nurse has tried to better understand his enigmatic and taciturn dad.

“This is a man I did not know very well,” Bissell said Saturday as he sat on the porch of his Pearl Street home. “I think I always believed that he loved me, but it was something that always came up in the context of things [problems] that would occur within our extended family.”

Bissell said he watches the news for the declassification of documents, in search of traces of his father’s work. Friends occasionally mention seeing the interviews his father gave on the PBS TV show Nova, and Bissell reads CIA histories for parallels between world events and things he witnessed.

Despite Richard Jr.’s having written a memoir of his time in the CIA, so much of him remains a mystery, said Richard Bissell III and his brother, 56-year-old Winthrop Bissell of Connecticut.

“He didn’t talk about work pretty much,” Winthrop Bissell said of his father. “He made it clear pretty early in the game, saying, ‘Well, if you hear anything at home, it stays here.’”

“My father was somewhat challenged by all of the duties of being a father. That was something that didn’t come easy to him,” Winthrop Bissell added. “He wasn’t quite the hands-on dad.”

“There had to be a piece of him that was cold to do what he did,” Richard Bissell said. “When you are in the business of getting a foreign leader out of a job — or killed — you have to be. But I think that’s in everybody.”

Yet deep feelings were not foreign to Bissell, his sons said. They were merely subsumed to the secrecy of spying and a powerful mind that devoured journals on foreign policy and economics. Bissell’s humanity was illustrated not with words, but in his gentle acceptance of others, his sly flashes of warmth and personal insight, and rare and sudden glints of temper that were as controlled as they were memorable.

“He under-reacted,” Richard Bissell III said, “but he did that with everything. A display of emotion was not his strong suit.

“This is a guy,” Bissell added, “that when we were kids looking at Playboy or Penthouse, was reading railroad timetables.”

Richard Bissell III said he found intriguing parallels between his father’s character and that of Edward Wilson, Matt Damon’s WASP-ish fictional character in the 2006 spy thriller “The Good Shepherd.”

Bissell was educated at Yale University, was deeply patriotic and as observant as he was reserved. He had a CIA telephone in a spare bedroom at home — though family members had to be elsewhere when his father occasionally shared cocktails with Dulles and other colleagues in the living room after work, his son said.

Bissell was solidly Republican, profoundly anti-communist, and often on secret trips around and out of the country. He was also one of the primary movers in the Bay of Pigs plot to depose Castro.

“The CIA,” Bissell said, “would have been proud of him for how little yapping my father did at home about his job. He was the model CIA employee in that regard.”

But unlike Damon’s character, Bissell studied history before becoming an economist. He was devoted to his wife and family, served in the War Shipping Administration during World War II — and he didn’t survive the fallout from the botched invasion. President Kennedy fired him.

“I remember that night when my father came home after it failed,” Bissell said. “He was very angry about that. I know he carried that failure around with him for the rest of his life.”

Bissell said his father admired Kennedy, who gave Bissell a medal and offered him another job within CIA. Bissell instead worked at the Institute for Defense Analyses, a Pentagon-funded think tank that evaluated weapons systems, and at United Technologies in Hartford, before he retired in the 1970s. He died in Farmington, Conn., in 1994.

“He always gave Kennedy credit for taking ultimate responsibility for the invasion,” Bissell said. “Then again, my father wasn’t the one dating Marilyn Monroe.”

Winthrop Bissell said he believes his father fell victim to one of the sad conundrums of the spy world: An operation is truly successful only when nobody knows about it. By that measure, Richard Bissell’s greatest contribution to his country’s survival in the nuclear age would be the many electronic and satellite operations he ran that the Soviets never caught, he explained.

Richard Bissell III was not scarred by his father’s emotional distance. If Bissell has any traumas, he said, they come from a car accident in 1981 that deprived him of his left eye and his 30 years as an emergency room nurse at EMMC, he said.

Bissell enlisted in the U.S. Army as a medic in the early 1960s and served with 90,000 troops stationed in the Dominican Republic. The contingent was part of U.S. efforts to support right-wing governments in Latin America and keep pressure on Castro, Bissell said.

He would have served in Vietnam, but his enlistment was almost gone, he said.

An admittedly poor student — he believes he had Attention Deficit Hyperactivity Disorder — Bissell had a variety of post-Army jobs and saw a rare burst of his father’s anger when he announced that he was quitting college.

Bissell and his father might clash today, if he listened to his liberal son’s condemnation of what Bissell calls the naivete that led to the U.S. wars in Afghanistan and Iraq.

Yet Richard Bissell Jr. never struck his children as a terribly intolerant man. He and his wife urged their children to be accepting of African-Americans, an unusual attitude in Segregated South of Washington, D.C. in the 1950s and ’60s, Winthrop Bissell said.

Almost all of Bissell’s five children inherited their idealism and commitment to public service, said Winthrop Bissell, who like his brother is a registered nurse.

Richard Bissell III shares much of his father’s independent spirit and intellectual power. He loves reading and analyticity and chooses his words with great precision, Winthrop Bissell said.

“He is a very warm person with a great sense of humor,” Winthrop Bissell said of his brother. “He has a great perspective on people and can look behind the scenes and see what they are like.”

Richard Bissell said he always had his father’s respect because he always paid his own way and took responsibility for his missteps. His father once told him as much, Bissell said.

And Richard Bissell Jr. must have been to his family something a spy must always be: a good listener. His son Richard had no trouble telling him of a near-scrape with the law or his first sexual encounter, at age 21. Bissell’s advice to his son on sex revealed just how much of an economist he really was.

“He said, ‘I want to tell you two things,’” Bissell said. “‘Don’t make a baby, and when it comes to it [sex], expend your interest, not your principal.’”

The younger Bissell’s only entry into the spy world came when he was a teenager. He and a friend planted three secret listening devices around the Bissell home, “plus one in the home of a next-door neighbor that I had the hots for,” he said.

Bissell told his father of the bugs in the house, and figures today that his father was secretly pleased with his son’s ingenuity. But as with so many things, his feelings remain a mystery, his son recalled.

“My father,” Bissell recalled, “never said a word about them.”