On the Set : Based on the Bizarre : ABC ADAPTS STORY OF FBI AGENT WHO ROMANCES AND THEN KILLS HIS INFORMANT

The plot of Monday’s ABC movie “Betrayed by Love” is so bizarre and sordid, it could only be based on fact.

Jeff Avery (Steven Weber), a handsome, ambitious, married FBI agent, has a torrid affair with his key informant, Deanne (Patricia Arquette). When she becomes pregnant with his child, Avery sees his life and career unraveling before his eyes. In a rage, he strangles Deanne, hides her in the trunk of his car and then throws her nude body off a cliff.

No one believes Avery murdered Deanne except her older married sister Dana (Mare Winningham), who goes on a one-woman crusade to bring Avery to justice. The FBI agent on whom Avery’s character is based is serving out a 16-year sentence in a federal prison and eligible for parole in 1998.

Arquette, Rosanna’s baby sister who starred in the 1993 features “Ethan Frome” and “True Romance,” doesn’t think “Betrayed by Love” is the typical true-life TV-movie fare audiences seem to crave. Besides, Arquette has a special fondness for TV movies.

“There’s something I loved about TV when I was little,” she says, puffing on a cigarette in an empty set at the Don Carlos Studios in Dwntown Los Angeles, where the production is filming this day. “We would say: ‘Let’s wait up and see the movie-of-the-week.’ It was very exciting. It was a big deal.’ ”

Nostalgia, though, wasn’t the only reason Arquette was drawn to the project. “First of all, it’s well-written,” she says shyly. “It has really good dialogue that was interesting to me.”

She also “felt” for Deanne. “I wanted her story to be told, but in a realistic way because she is a real person. You know, she does things that are not ‘good’ or ‘attractive.’ She is confusing, but she’s a real person. What it boils down to is that it’s never OK to kill someone.”

There’s also a little bit of Deanne in Arquette. “Yet I know with my moral code, certain things could drive me to murder. She’s somebody who has a really hard life and not a good situation and is looking for something more. She has two kids and lives with her ex-husband. She’s collecting welfare from two different states.”

And Deanne, who feels trapped in her small Southern hometown (the real events occurred in Kentucky), is something of a free spirit. “She has her own sexuality. It’s not really acceptable in this society. She wants more. The man she falls in love with, he is also very forward-motivated, too. I think that is attractive for her to meet a man who is looking for more in the world.”

Like Arquette, executive producer Edgar Scherick was impressed with Alan Sharpe’s script. But primarily he fell in love with Deanne. “She has such a devil-may-care attitude about everything,” he says. “She had an essential honesty about her own needs. She seemed like an essentially honest, desirably funny kind of tragic kind of character.”

The Emmy Award-winning Winningham (“Amber Waves”) was eager to work with Arquette because she’d been a fan since Arquette’s role as a pregnant wife in Sean Penn’s 1991 film “The Indian Runner.”

But Winningham almost didn’t do the film because it was a fact-based drama. “I have a hate-hate relationship with true stories,” she explains between takes.

Four years ago, Winningham got her first taste of docudrama when she starred in the ABC movie “Love and Lies,” in which she played an undercover cop who falls for the man she’s trying to send to jail. Though she vowed then she’d never do another drama of that genre, Winningham liked the “Love and Lies” script, which also was written by Sharpe.

“That had some of the best writing I have ever had the opportunity to act. When I heard he wrote this, I was interested.”

In a perfect world, Winningham says, true-life stories wouldn’t become TV movies. “People are making money. It’s not the people who are selling themselves. I understand their reasons for that, but there are all sorts of people who are brought (into the project). I had a little bit of a close encounter (with the real person) on ‘Love and Lies.’ ”

She avoided talking or meeting with the real Dana. “I’m sure something would give me the willies and I would question why I did it. If I talked to somebody, somebody would end up saying: ‘I had no say in my life being exploited this way.’ I personally would just go crazy.”

Arquette, though, did as much research as she could. “I would have liked to have done a lot more, but I wasn’t allowed for legal reasons,” she says. “I care a lot about it being a real story. Not that I wanted to do a docudrama and run around saying everything exactly the same. But it’s nice to check things out as much as you can, so that you can explore and get a feeling of someone’s spirit, someone’s heart. Why they needed what they needed. What they looked at in the morning when they woke up.”

“Betrayed by Love” airs Monday at 9 p.m. on ABC.