Lauren Bacall, Humphrey Bogart had 'emotional affairs' but remained 'devoted to each other': author

The power couple of Hollywood's golden era is the subject of a new book by William J. Mann, 'Bogie & Bacall: The Surprising True Story of Hollywood's Greatest Love Affair'

Lauren Bacall and Humphry Bogart’s passionate romance is still recognized as one of Hollywood’s most legendary love stories, but it wasn’t always marital bliss.

Author William J. Mann has written a book on the power couple that was recently published, "Bogie & Bacall: The Surprising True Story of Hollywood’s Greatest Love Affair." In it, he alleged that the pair had once been "emotionally unfaithful" to each other, their significant age gap being a major factor.

In painting an honest portrayal of the couple's marriage, the Hollywood historian spoke to several surviving insiders and had access to never-before-seen documents.

Bacall, one of the last stars from Hollywood’s golden era, died in 2014 at age 89.

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Bogie and Bacall book cover

William J. Mann, author of "Bogie & Bacall," spoke to some of the last living insiders who knew the couple and had access to never-before-seen papers. (Harper)

"When we talk about great love stories, we think of them in fairytale terms," Mann told Fox News Digital. "You know, ‘And they lived happily ever after,’ as if there weren’t going to be challenges, there weren’t going to be conflicts. When you make a life with someone, it’s about learning how to compromise, learning how to find a way forward together despite what are going to be some differences."

"And they did have their differences," he shared. "Especially in the beginning when Bacall was struggling to be more than just Mrs. Bogart. The relationship was romantic. It was loving, it was committed. But it was not always emotionally faithful."

"I think… they were emotional relationships, emotional affairs," Mann claimed. "You can be emotionally unfaithful to your spouse."

Bacall, a fashion model, moved to Hollywood from New York when she was 19. She achieved immediate fame in 1944 with one scene in her first film, "To Have and Have Not." Leaving Bogart’s hotel room, the starlet purred, "You know how to whistle, don’t you, Steve? You just put your lips together and blow."

A close-up of Lauren Bacall

Lauren Bacall was a 19-year-old fashion model from New York City when she moved to Hollywood. (Kobal Foundation/Getty Images)

Bogart, who was married to his third wife, actress Mayo Methot, became Bacall’s lover when cameras stopped rolling. He was 25 years older than her.

"Bogie became her champion, her protector," Mann explained. "And I think that sense of him needing to take care of her and protect her really endeared her to him. … And their feelings quickly turned into love."

The blossoming romance "terrified" Bacall, he said. Such a scandal would destroy her career before it even started.

Humphrey Bogart and Lauren Bacall embracing and kissing while filming a scene from their film

Lauren Bacall is embraced by Humphrey Bogart in a scene from the film "To Have and Have Not," circa 1944. (Warner Brothers/Getty Images)

"It was known at that point that Bogart’s marriage was disintegrating," said Mann. "They were known as the ‘Battling Bogarts.’ But, at the same time, Bacall wanted to make sure the public wouldn’t blame her or wouldn’t see her as a femme fatale. Bogie was also very concerned. He didn’t want to lose his position in Hollywood, but he also didn’t want to lose her. In the beginning, there was a lot of nervousness. … But they were yearning to be together."

Bogart returned to Methot several times before realizing his marriage couldn’t be saved. In 1945, Bogart married Bacall. He was 45, and she was 20.

According to Mann, it didn’t take long for their marriage to be tested.

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Humphrey Bogart posing next to a plane and his wife Lauren Bacall in formal wear

Actor Humphrey Bogart (1899-1957) and his wife, actress Lauren Bacall, pictured as they board an American Airlines Flagship at LaGuardia Airport In New York, circa 1952. Bogart and Bacall were en route to Boston, where they were taking part in a rally for Adlai Stevenson's presidential bid. (Pictorial Parade/Archive Photos/Getty Images)

In 1952, the couple became supporters of Adlai Stevenson during the 1952 presidential election. The governor of Illinois was running as a Democrat opposite Republican Dwight D. Eisenhower.

"Bacall was always a liberal Democrat," Mann explained. "Bogie was originally for Dwight Eisenhower [but] eventually came over to Stevenson’s side as well. … And she got campaign fever. Many people who’ve been in political campaigns understand that … you get this adrenaline rush. It was nothing she had ever experienced before. And because I think she thought she was working for … a higher purpose, this took on even greater meaning for her than making a movie."

Lauren Bacall wearing a white shirt as she sits on Humphrey Bogarts lap

Lauren Bacall was 20 when she married Humphrey Bogart in 1945. He was 45. (John Kobal Foundation/Getty Images)

"She comes out and says in her memoir, ‘I was far away from Bogie. All I was thinking about was Stevenson,'" Mann shared. "And in Bogie’s papers, I found notes from him to [director] John Huston where he’s clearly uncomfortable by his wife’s infatuation with this political candidate. And it got very intense."

Lauren Bacall wearing a dark dress and smiling next to Adlai Stevenson

Democratic leader Adlai Stevenson is seen here chatting with Lauren Bacall at a Jefferson-Jackson Day dinner in Los Angeles prior to his radio-television speech. The dinner was attended by more than 1,000 Democratic luminaries. (Getty Images)

In her memoir, Bacall wrote, "At every speech from the beginning — every platform, breakfast, lunch — Stevenson would catch my eye and wave and smile at me. To my fantasizing mind, he seemed so vulnerable."

"Bogie said he had a funny idea for a cartoon," the mother of two shared. "He’d be standing at our front door with a child on each side and rain falling heavily and [my son] Stephen would say, ‘Daddy, where’s Mommy?’ Bogie, looking sadly into space, would reply, ‘With Adlai.’ It was a funny idea and I laughed, but Bogie knew I had been deeply affected by Stevenson and, for that matter, he had too."

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Adlai Stevenson holding telegrams

Gov. Adlai Stevenson of Illinois beams over a few of the thousands of telegrams he found as he returned to his desk at Springfield. (Getty Images)

Mann insisted in his book that Bacall and Stevenson "had become quite close" and "she was rarely far from his side, with Bogie somewhere in the background." He stressed that the relationship was never physical, but "it was definitely an affair of the heart."

WATCH: LAUREN BACALL, HUMPHREY BOGART HAD EMOTIONAL AFFAIRS, BUT REMAINED DEVOTED TO EACH OTHER: AUTHOR

"She loved Bogie," said Mann. "But Stevenson was awakening some part of herself that she had never known before. The relationship continued through the end of the campaign. He lost in a landslide, and she was devastated. She tried to keep in touch with him, but it became increasingly difficult. My take on it, looking back all these years, is that she was more into him than he was into her. … She finally realizes [this] and retreats. But in many ways, I think it was the most intense, emotional and intellectually stimulating relationship of her life."

In her memoir, Bacall vividly remembered when Stevenson lost.

Lauren Bacall in a glamorous dark dress next to Humphrey Bogart in a bow-tie

Despite their marriage being tested, Humphrey Bogart and Lauren Bacall remained devoted to each other. (Getty Images)

"I adored Adlai Stevenson, I supposed I even worshipped him," she wrote. "He instilled that feeling in many — loyalty, adulation. He brought out the best in me, or at least I thought he did. He made me feel I knew more than I actually did, that I was valuable. He broadened my horizons, made me more aware of human dignity and the plight of people everywhere. Until Adlai Stevenson, I was a perfectly happy woman with a husband whom I loved — a beautiful son and daughter — not a care in the world. His entrance into my life shook me up completely."

American actors Lauren Bacall and Humphrey Bogart on the set of To Have and Have Not,

Humphrey Bogart and Lauren Bacall shared two children. (Sunset Boulevard/Corbis via Getty Images)

"In my usual way, I romanticized," she continued. "He needed a wife, obviously … but he needed someone to share his life with. I fantasized that I would be a long-distance partner — a pen pal — a good friend whom he could feel free to talk to about anything. A sympathetic, non-judging ear. It took me a long time to dissect my feelings, but, at the moment, I felt a combination of hero worship and slight infatuation. This campaign had disrupted my life completely."

Mann says Bogart had his own emotional affair.

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Verita Thompson sitting on Humphrey Bogarts lap while they read a letter.

Verita Thompson later wrote about her relationship with Humphrey Bogart in a book, "Bogie and Me." (Harper)

"I was very fortunate to speak with the surviving partner of Verita Thompson," he explained. "She was a wigmaker in Hollywood. … She made Bogie’s wigs for him because he was starting to lose his hair very early. Before Bacall, they began an affair while he was still married to his third wife. It was an incredibly close and loving relationship. They weren’t that far apart in age. … They both liked to drink — they could hold their liquor. They loved to sail. They had a lot in common."

Humphrey Bogart holding Mayo Methots cigarette

Humphrey Bogart was married to Mayo Methot from 1938 to 1945. (Getty Images)

According to Mann, Thompson, who also went by Vera, believed Bogart would divorce Methot and propose because "they had talked about getting married." But when he quickly moved on to his much younger, more glamorous co-star, she was "devastated."

"They eventually reconnected," said Mann. "And I think, at that point, the relationship was most likely emotional. … I think especially as Bacall was finding her own world, her own life, her own friends, people like Adlai, Bogie turned more and more to Verita. They would go sailing together on his yacht. … She began coming to the house. She would trim his children’s hair. She was part of the family in many ways. Bacall knew about her. I don’t think she was ever fully comfortable with her, but she knew that relationship was very important to Bogie."

Actress Lauren Bacall and Humphrey Bogart in a scene from the movie"Dark Passage"

Verita Thompson was said to be devastated after Humphrey Bogart moved on and married his younger, more glamorous co-star, Lauren Bacall (pictured here). (Donaldson Collection/Getty Images)

"But these relationships never threatened the primary bond between husband and wife," Mann insisted.

Bacall and Bogart remained devoted to each other, especially as the actor battled cancer. The actress became a doting caregiver.

A close-up of Humphrey Bogart sitting next to Frank Sinatra

Humphrey Bogart was diagnosed with cancer in 1956. Despite a successful surgery, the cancer returned, and he died in 1957 at age 57.  (Earl Leaf/Michael Ochs Archives/Getty Images)

"She's sitting with him in the hospital, and his stitches are coming undone," said Mann. "She's trying to hold the stitches together on his abdomen. She sleeps with him when he's about 80 pounds, because he tells her, 'Don't leave me tonight.' ... Of course, she doesn't sleep all night. She's awake. You don't do that if you don't really love somebody. Even with the emotional indiscretions ... those last several months of Bogie's life prove how much she loved him."

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Lauren Bacall looking up at her husband Humphrey Bogart in their home

Lauren Bacall stood by Humphrey Bogart as he battled cancer. (John Kobal Foundation/Getty Images)

Bogart died in 1957 at age 57.

"I fairly often have thought how lucky I was," Bacall reflected to Vanity Fair in 2011. "I knew everybody because I was married to Bogie, and that 25-year difference was the most fantastic thing for me to have in my life."

The Associated Press contributed to this report.