A 69-year-old grandmother and retired church administrator has come forward with explicit details of an 18-month affair she claims to have carried on with President John F. Kennedy — when she was a 19-year-old intern at the White House. Mimi Alford recounts the salacious details in her "explosive" tell-all memoir Once Upon a Secret: My Affair with President John F. Kennedy and its Aftermath. In the book, which was released Wednesday, Alford says that she always called Kennedy "Mr. President," and that they never kissed on the lips. "The fact that I was being desired by the most famous and powerful man in America only amplified my feelings," she writes. "That's why I didn't say no to the president." Many experts are taking Alford's claims seriously: "I would tend toward accepting [the story] until it's proven otherwise," presidential historian Doug Wead tells ABC News. Here, four of Alford's raciest claims:

1. She lost her virginity in the first lady's bedroom
Four days into her internship, Alford claims that the president invited her for a midday swim at the White House pool, where he seduced her. Kennedy invited Alford to a party later that evening with aide Dave Powers and other young staffers, frequently refilling her drink before inviting her up to Mrs. Kennedy's bedroom, Alford claims. There, they had sex — her first time — after which Kennedy promptly returned the party. "I was in shock," she writes in an excerpt published by the New York Post. "He, on the other hand, was matter-of-fact, and acted as if what had just occurred was the most natural thing in the world."

2. Alford was asked to service JFK's friends
"The affair isn't the only salacious story in the book," says Matt Negrin at ABC News. In another passage, Alford claims that Kennedy asked her to perform oral sex on Powers while they were in the pool. "The president swam over and whispered in my ear. 'Mr. Powers looks a little tense,' he said. 'Would you take care of it?'" Alford assented. "I'm ashamed to say that I did. …The president silently watched." At a Boston fundraiser attended by Ted Kennedy, Alford says the president asked, "Mimi, why don't you take care of my baby brother? He could stand a little relaxation." This time, she refused. "Absolutely not, Mr. President."

3. He flew her around the country
Alford's internship only lasted a summer, but the affair continued when she returned to school at Wheaton College in Massachusetts. She alleges that JFK would call under the pseudonym "Michael Carter," and invite her to Washington to see him when Mrs. Kennedy was away. One such visit came during the defining moments of the Cuban missile crisis. Another was just days after Jackie had miscarried. Their final dalliance — during which Alford was engaged to be married — occurred in a New York hotel just seven days before the president was assassinated in Dallas.

4. The president gave her drugs
Kennedy invited Alford to a "wild party" at Bing Crosby's desert ranch, and allegedly forced her to try amyl nitrate — better known as "poppers." The chemical compound raises the heart rate, and is commonly used to enhance sex. Kennedy didn't try them, she says, but he held the amyl nitrate under her nose against her will, after which she ran from the room crying.