Emily Watson goes into the darkness for ‘Appropriate Adult’

When Emily Watson heard she was being sent a script for “Appropriate Adult,” she was wary. The made-for-TV movie, which premieres Saturday on Sundance Channel, depicts the real-life relationship between British serial killer Fred West and Janet Leach, a social worker in training who was asked to sit in on police interrogations as an “appropriate adult,” a role in the United Kingdom legal system meant to safeguard the rights of young people and vulnerable adults in police custody.

That was how Leach, a Gloucester housewife, found herself in a room on Feb. 25, 1994, as West matter-of-factly talked about strangling and dismembering his daughter. Leach eventually sat in on 40 interviews as West revealed depraved details of the Cromwell Street murders — at least 12 young women and girls killed by West (and his wife Rosemary West) — in one of the biggest police investigations in British history.

Watson has been uncompromising in her career, choosing offbeat roles and frequenting independent films; she found success early on playing disturbed characters in “Breaking the Waves” and “Hilary and Jackie.” But the extremity of the West case unnerved her.

“It’s obviously a very sensitive subject matter,” she said in a phone interview. “When there are crimes of a sexual nature — murderous crimes of a sexual nature — it’s very, very difficult material. But I think it’s important to investigate those really dark parts of our society and discover how human beings get to that point and just live amongst us and prey on people.”

Written by Neil McKay, “Appropriate Adult” examines the curious connection between Leach and the often-charming killer, played by Dominic West (best known for his role as Det. McNulty on HBO’s “The Wire”).

“The murders were so notorious you couldn’t help but be aware of them,” Watson said. “But I had never heard of her and what I learned was so absorbing. It was not like anything I’ve ever done before.”

It’s also markedly different from anything she’s appearing in these days. The two-time Oscar nominee will star in Steven Spielberg’s upcoming Oscar-buzzed WWI epic, “War Horse.” And she can also be seen in the small film, “Oranges and Sunshine,” based on British social worker Margaret Humphreys’ book “Empty Cradles,” about her mission to help 130,000 British children, secretly deported to Australia and other British colonies, find their families.

Before meeting Leach, Watson studied transcripts and the countless interviews producers had conducted with her.

“I only spent an afternoon with her,” Watson said. “In a way, when I met her, I didn’t want to sit there and go ‘so what happened when you did this?’ or ‘Why did you do this?’ I really just wanted to feel what her center of gravity was and see the look in her eye and how she was as a person. She’s very interesting. I almost expected her to be timid and broken. I think she’s recovered a lot since then. I think she’s much stronger now than she was. She was sucked in.”

Fred West is portrayed as a charismatic personality who was both drawn to his appropriate adult and drew her in, requesting Leach’s presence and sometimes confiding horrifying details to her when they were alone — seemingly playing on her sympathy and humanity and exploiting the duty of confidentiality she owed him, preventing her from telling police. McKay chose to focus on West’s psychological grip over Leach rather than the violent murders themselves.

“The more we researched it, the more we realized how extraordinary her story was,” he said. “It’s a way of dealing with a sensitive subject without getting caught up in blood and gore and sensationalism.” Leach is the viewers’ representative on-screen, he added. The camera often focuses on her undiscerning expression as West denies or reveals his crimes to police.

That’s not to say the movie wasn’t met with some scorn. Controversy began rumbling around “Appropriate Adult” before its airing in Britain in September, where it drew more than 4 million viewers: One of Leach’s sons, as well as one of West’s daughters, spoke out against the project to outlets in Britain. And victims’ families also spoke of being nervous about how the gruesome case would be dramatized for TV. And like Watson, Dominic West also expressed having reservations about being a part of the project initially.

“Had it been about him and his point of view, it’s essentially pornography or horror,” he said. “She was one of his victims. She sat in these hundreds of hours of interviews, then her job was over. But it really wasn’t. She then continued to visit him in prison and do his laundry and things like that. Which is pretty shocking really. But she was just so fascinated by him.”

It was easy to see why, the actors said. West and Watson, having studied footage and recordings of Fred, both noted his ability to manipulate. “There are lots of photographs of him with police — the police are often laughing and smiling,” West said. “There was a disconnect for him, though. He’s talking about chopping up his daughter like chopping wood or putting the trash out.” In one instance — depicted in the movie — upon being told police have found a thigh bone in his garden, he responds quizzically, “ ‘Can’t think how that got there.’ ”

Fred West would ultimately commit suicide in 1995 while in custody after being charged with 12 murders — his catalog of crimes also including rape, abduction and child cruelty.

“It’s so bizarre,” Watson said in reflecting on West’s intense relationship with Leach. “I can’t understand it. I don’t know if that would happen to me. I don’t think I would be able to get close to somebody like that. But I guess you don’t really know how you’d behave in that situation until you’re in it.”

yvonne.villarreal@latimes.com