Monica Lewinsky details Bill Clinton sexual encounter that led to stained blue dress

Monica Lewinsky is opening up about her affair with former President Bill Clinton in a new A&E series called "The Clinton Affair."

In a preview clip detailed by the New York Post, Lewinsky explains how that stain on her infamous blue dress -- the dress that proved her affair with the then-president -- came to be.

Somewhere in the early months of 1997, after Clinton had won reelection in 1996, the president invited Lewinsky to a White House radio address, he gave her a present via his personal secretary, Betty Currie.

"She brought me into the Oval Office and all three of us went into the back study, and she went into the dining room to hide there," Lewinsky recalled. "Because the illusion to everyone else was that I was not alone with him."

The present from Clinton was a hat pin, because he thought she "always looks so cute in hats," as well as a copy of "Leaves of Grass" by Walt Whitman.

"It was a very meaningful present to me," she explained in the special. "It’s an intimate book that you don’t give lightly. Whatever had been nagging in me -- is what I’m feeling real? Is that there? Whatever those insecurities were, they kind of vanished in some way with him giving me this gift."

Lewinsky goes on to detail their first sexual encounter since she had been "banished" to the Pentagon.

"We moved to the bathroom and were more intimate. There was some attention paid on me and then I was reciprocating, where up until that point he had always stopped before completion on his part," she said. "I sort of stood up and said I wanted to move past that stage and so he finally said okay."

"So that finished and then I hugged him after, and he hugged me," she went on. "And off I went."

Lewinsky didn't notice the stain on her dress stemming from the encounter, and neither did anyone else at a dinner she attended that same night.

"None of these people said to me, ‘Hey, you’ve got to go to the bathroom, you’ve got stuff all over your dress,'" she remembered. In fact, she didn't notice the stain until Thanksgiving of that year -- months later -- when she tried it on for Linda Tripp, who was secretly recording her at the time and told her she looked fat in the dress.

Tripp advised Lewinsky to hold on to the stained blue dress.

"The Clinton Affair" premieres on Sunday, November 18, on A&E