Not because "Waitress" is sad - it isn't that kind of movie - but because its writer-director and co-star, Adrienne Shelly, won't be there. In a shocking act of violence, Shelly was slain in November in her New York office. A construction worker awaits trial in the killing.

Shelly's film, which she had already submitted to Sundance, was accepted by the festival after her death.

"The last thing we actually spoke about was Sundance and how excited we were [at the prospect of coming to Park City]. She was so happy," said the film's producer, Michael Roiff, in a recent phone interview. "Her death was an unbelievable shock. It's the most horrible thing I've ever been involved with in my life."

Many in the cast and crew were stunned by the news of Shelly's death. Police believe Shelly was killed by Diego Pillco, a 19-year-old undocumented worker from Ecuador, after she complained about noise he was making in the apartment below her West Village office and threatened to call police.

According to news reports, Pillco confessed to killing her during an argument, then hanging her body with a bedsheet from the shower-curtain rod to make it look like a suicide. He is currently in jail awaiting trial.

Shelly, 40, grew up in New York and worked as an actress in independent films, in off-Broadway plays and in guest spots on such TV series as "Law & Order."

She was probably best known for her starring roles in indie filmmaker Hal Hartley's "The Unbelievable Truth" (1989) and "Trust" (1990). Shelly had directed two previous feature films, but "Waitress" is the first of hers to screen at Sundance.

Filmed in late 2005 near Los Angeles, "Waitress" stars Keri Russell (TV's "Felicity") as Jenna, a waitress in a cheery Southern diner. Jenna feels trapped in a miserable marriage to her needy, jealous husband (Jeremy Sisto), so when the film begins, she's not thrilled to learn that she's pregnant. We know this because Jenna makes a ham-and-brie quiche for the diner - she has a gift for baking - and names it "I-Don't-Want-Earl's-

Baby-Pie."

Complicating things further is the town's handsome new gynecologist (Nathan Fillion), with whom Jenna begins a passionate affair. The movie maintains a slyly humorous tone throughout, aided by witty performances by Cheryl Hines (''Curb Your Enthusiasm'') as another waitress and Andy Griffith as the diner's cantankerous owner.

Shelly has a supporting role as Dawn, a waitress pal of Jenna's. She originally wrote the lead role for herself when she was pregnant with her daughter in 2003.

"I was really scared about the idea of having a baby," Shelly said in publicity notes compiled for the film. "I was terrified, and I really had never seen that reflected in anything, not in a book or in a movie. People don't talk about those kind of fears, but I know how large they loom. It's almost like a sacrilege to say that becoming a mother is scary. So I wanted to write a movie about those fears and give them a voice."

Russell, who has played a pregnant woman in four recent movies, said she was drawn to Jenna's on-screen journey from unhappy wife to giddy adulteress to adoring new mom. She also liked Shelly's forthright approach to directing.

"She knew exactly what she wanted," said Russell by phone from Los Angeles. "She just got right to the point - 'Do that, don't do that' - which I appreciated."

Shelly is survived by her husband, Andrew Ostroy, and their 3-year-old daughter Sophie, who appears in the final scene of "Waitress" - a scene that now packs an unintended poignancy.

"It still doesn't feel real to me," said Russell, who will be in Park City this week along with many others from the film's cast and crew. "And it probably won't until we're at Sundance watching the movie and she's not there. The whole situation is very surreal."

Roiff, who visited the set of "Waitress" every day and spent hours with Shelly in the editing room, said Shelly was proud of how the movie turned out. Although "Waitress" does not yet have a theatrical distributor, Roiff believes the film has commercial appeal.

As a show of support, he and the cast will stand in for Shelly during the Q&A sessions that follow each Sundance screening.

"This is such a bittersweet time," he said. "I miss her. But I spend most of my time dwelling on how lucky I was to work with Adrienne. She made the film that she dreamt of."

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* BRANDON GRIGGS can be contacted at griggs@sltrib.com or 801-257-8689. Send comments about this story to livingeditor@sltrib.com.