If you stick around through the closing credits of Before Midnight, the latest film in the trilogy that also includes Before Sunrise and Before Sunset, you’ll see that the movie is dedicated to someone whose name even the most die-hard fans have never heard before: Amy Lehrhaupt. Almost 25 years ago, Lehrhaupt met a young man named Richard Linklater and spent a night with him that he never forgot. Their encounter inspired Linklater to conceive and direct Before Sunrise, the first film in the series. She never saw it, though; unbeknownst to Linklater, by the time that movie came out, Lehrhaupt was dead.

Linklater never mentioned Lehrhaupt by name in the press before promoting Before Midnight—Ethan Hawke has said that the director was uncomfortable mentioning her until “extremely recently”—but he has long made brief references to their encounter. From a number of interviews he’s done over the years, we can now piece together the complete story of how Lehrhaupt helped inspire the series.

Linklater met Lehrhaupt in fall 1989, when he was visiting his sister in Philadelphia. He was 29 and had just finished shooting Slacker, and was staying there for one night while passing through on the way home from New York. Lehrhaupt was several years younger, about 20. They met in a toy shop, and ended up spending the whole night together, “from midnight until six in the morning,” “walking around, flirting, doing things you would never do now.” As in Before Sunrise, most of what they did was talk, “about art, science, film, the gamut.” Did they kiss? Yes. Did they have sex? The Times went so far as to ask Linklater in a recent interview, but he said he wants to “leave a little mystery.”

Even in the midst of that romantic night, the filmmaker in Linklater couldn’t help but consider its cinematic possibilities. In a 2004 interview with the New York Times, he remembered “walking around [thinking], ‘If I could just capture this feeling I’m having right now,’ instead of actually having that feeling.” On a recent episode of the podcast The Q&A with Jeff Goldsmith, he recalled mentioning the movie idea to Lehrhaupt that night:

Even as that experience was going on … I was like, “I’m gonna make a film about this.” And she was like, “What ‘this’? What’re you talking about?” And I was like, “Just this. This feeling. This thing that’s going on between us.”

But as the night came to an end, the paths of Linklater and Lehrhaupt began to diverge from the fictional storyline of Jesse (Ethan Hawke) and Céline (Julie Delpy). In fact, on The Q&A, Linklater revealed that the ending of Before Sunrise was in part a response to what happened with him and Lehrhaupt. Unlike Jesse and Céline, who agree to reconvene in six months, the real-life young lovers exchanged numbers and tried to keep in touch while they were away. They called each other a few times, but it was “that long distance thing” that did them in. “It sort of did the fizzle,” he says, “So in the first movie that was a thing, the idea that they would intellectually kind of get beyond that and say ‘Well, we’re on different continents. What are the odds that it’s gonna work. Let’s just commit to this night.’ ”

Linklater soon became involved with another woman, who “swept into [his] life … and took over for about a year or so,” and he and Lehrhaupt never talked again. He did think that maybe “she would show up at a Before Sunrise screening or something.” In Before Sunset, Céline shows up at a reading of Jesse’s book This Time, which is based on their night together. “It would be so weird,” he said, in 2004. But she never did.

Linklater didn’t know then that Lehrhaupt had died in a motorcycle accident on May 9, 1994, before she reached her 25th birthday. Before Sunrise started filming a few weeks later. Linklater only learned of her death three years ago, when a friend of Lehrhaupt’s, who knew about the encounter, put it together and sent him a letter. “It was very sad,” Linklater told the Times. Ethan Hawke was similarly devastated when he heard it, though he reminded Linklater that if he hadn’t met her, then he never would have made these movies or met some of the people who worked on them with him. “Who knows how we reverberate through each other’s lives,” Linklater reflected in another interview, “But she’s an inspiration on this.”

In this way, Linklater did find another way to make that feeling, that “thing in the air” they once had between them, last: He turned it into cinema.