Some of us feel as if we have grown up with Jesse and Celine; at the least, they have grown up with us. In Before Sunrise, in 1995, they were young and gilded backpackers who met in Vienna and wandered around all night, talking about anything just to stay together. Nine years later, they met again in Paris in Before Sunset. Immediately drawn to each other again, they sparred all day until Jesse was supposed to fly home to Chicago. Did he take that plane? The question was left hanging. Now, after another nine years, they're back. The third film in the series, Before Midnight, is also about walking and talking and nothing much happening, but it is as dark as its title suggests. Jesse and Celine are together; they have twins as a result of that night in Paris; they love each other; they still fill their lives and our screens with loose, clever talk. Nine years together, however, are nothing like nine years apart. Jesse feels guilty about his son left in Chicago; Celine resents the long stretches she spent parenting alone while Jesse, now a writer, swanned around on publishers' tours. On an idyllic holiday in Greece - statistically, holidays are a testing time for marriages - guilt and enduring resentments bubble to the surface of all that talk. They are 41 now. It's not all about flirting. The Before series is the brainchild of director Richard Linklater, who made his name in 1993 with Dazed and Confused and most recently made Bernie, a bleak comedy that earned Jack Black a Golden Globe nomination. Recently, Linklater admitted the original story for Before Sunrise came from his life: in 1989, he spent a night in Philadelphia talking to Amy Lehrhaupt, to whom this film is dedicated. He wrote a draft, then asked actors Ethan Hawke and Julie Delpy to work on it with him. ''I said: 'We are going to rewrite this script and you guys are going to bring a lot of yourselves to these characters,''' he says. ''And they did. I think the three of us have created these two characters and so we all kind of have dominion over all of them. I'm both and they are sort of both. If an idea comes from one of us, it will filter through the other two; we will rewrite it or go deeper. If one of us doesn't like it, it isn't in the movie. It's a very fluid collaboration.'' They all stress this was writing, not improvising. Hawke has two well-reviewed novels to his credit; Delpy has directed four features and thinks of herself as a director more than an actor. Hawke and Delpy do interviews together, talking over each other constantly. Many people assume they really are a couple. ''We're not!'' Delpy says immediately. No, Hawke cuts in, but he understands why people want to think so. ''You go watch Before Midnight and in the back of your mind is an image of these people 20 years ago. So it has a subconscious to it; it's powerful.'' In this third episode, Hawke says, the trio wanted to explore the daily stress of a real relationship. ''We couldn't have them miss each other again and meet in their 40s,'' Delpy says. ''Then it would be about cheating. It makes more sense with the end of the last film, when he was so unhappy in his marriage, if they are together. So we just had to be true and, yes, when you are with someone for eight years, it becomes something else. Love is not just one thing. It is a lot of things.'' ''The first two play on fantasy, on a romantic ideal,'' Hawke says. ''We were interested in a fight without a clear villain. We are so used to seeing either these idealised relationships or couples who are fighting and are just so mean to each other. What I feel proud of here is that they are just real people. Nobody is a horrible alcoholic; nobody has ruined the other one's life; nobody is abusive. But it's still hard. They love each other, they want the best for each other and they are fighting like cats and dogs. The absolute banality of that interests me.'' At the Cannes Film Festival, the audience was siding with Jesse; Celine's quick rages drew clicks of irritation. When the film was unveiled at Sundance in January, Linklater says, it was the opposite. This is despite his conviction the film is ''male-female neutral''. Hawke isn't surprised. ''It's like they're friends with the couple,'' he says. '''She is really being too demanding about that!' 'But he's an immature prick who needs to grow up!''' Delpy chips in: ''I think that is a sign of success in its own way, that people take sides. And it's fine to play someone who is a bit exasperating at times. Not perfect, not a Hollywood representation of a woman with no flaws.'' During the months they worked together, the three writers watched the earlier films and filled in those decade gaps with children, jobs, old arguments, everything. ''It's a whole world,'' Delpy says. ''That is the largest thing we did,'' Hawke agrees. ''Sit around saying, 'How did that happen? What happened then?' You have got to figure out what the hell their lives look like or the argument will be a sitcom argument.'' Before Sunrise, Before Sunset and Before Midnight span 18 years but, as Hawke points out, the time-frame for each is so short that they add up to less than a full day. When they started work on Before Sunrise, they had no idea they would keep coming back to Jesse and Celine. They have no idea now whether they will walk and talk their way through another film when the couple turns 50. For those of us who have grown up with them, let's hope so. What came before Before Sunrise (1995) Jesse meets Celine on a train to Vienna; she is on her way home to Paris, while he is about to catch a cheap flight back to the US. He persuades her to stop off in Vienna with him and they spend the night walking around the city, where they encounter the odd eccentric - an elderly vagrant offers to write them a poem, for example - and steal a kiss on the wheel made famous by The Third Man. The script, written by director Richard Linklater with actor Kim Krizan, was heavily reworked when Linklater found his stars after a nine-month search. The film won a Silver Bear for best director at the Berlin Film Festival and almost universally rapt reviews. Before Sunset (2004) Nine years later, Celine turns up at the famous Shakespeare bookshop in Paris where Jesse is doing a reading from his new book Just in Time, which is clearly based on their first encounter. Again, he is due to board a plane; they must make the most of the hour they have to tell each other what is happening in their lives. Both are in unhappy relationships. This time Delpy and Hawke were credited as scriptwriters with Linklater and Krizan; all four were nominated for an Oscar for the screenplay. Three's company Behind the onscreen couple and their director. Julie Delpy Born in Paris, France, in 1969 to an avant-garde theatrical family. Personal life Moved to the US in 1990. Living in Los Angeles, she became a US citizen in 2001. Has one child with German film composer Marc Streitenfeld. Career markers First cast at age 14 by legendary director Jean-Luc Godard in Detective. Nominated for a Cesar, the French equivalent of an Oscar, at 16. Was Krzysztof Kieslowski's first muse in the Three Colours series (1993). US breakthrough came in An American Werewolf in Paris (1997). Other strings to her bow Directed five features, four released internationally; 2 Days in Paris (2007) and 2 Days in New York (2012), in which she also starred with Chris Rock, were applauded by critics. Released a self-titled album of her own songs (2003); three tracks from the album were used in Before Sunset. Ethan Hawke Born in Austin, Texas, in 1970. Personal life Married to actor Uma Thurman 1998-2004; two children. Married to Ryan Shawhughes since 2008; two children. Career markers During high school, he persuaded his mother to let him audition for Explorers (1985), a sci-fi film with River Phoenix. Dropped out of university at 18 to star in Peter Weir's Dead Poets' Society(1989) with Robin Williams. Has since concentrated on art films and classical theatre, but was nominated for a best supporting actor Oscar for the cop drama Training Day (2001). Other films includeReality Bites (1994), Gattaca (1997), Before the Devil Knows You're Dead (2007). Other strings to his bow Wrote novels The Hottest State (1996) and Ash Wednesday (2002). Directed the films Chelsea Walls (2002) and his own adaptation of The Hottest State (1996). Richard Linklater Born in Houston, Texas, in 1960. Personal life Divorced. Lives in Austin, Texas. The cinema society he started helped make Austin a centre for cool filmmakers. Career markers Defined a Gen X state of mind with his second film, the ultra-low-budget Slacker (1991). Further defined it with Dazed and Confused (1993), a high school ensemble comedy. Made slackerdom commercial in School of Rock (2003), starring Jack Black. Other films include Fast Food Nation (2006), Me and Orson Welles (2009) and Bernie (2011), the top-rated comedy last year on the Rotten Tomatoes review website. Before Midnight is out on Thursday.