On the surface it might seem that “The Deep End,” a contemporary thriller in which Tilda Swinton plays Margaret Hall, a Nevada mother desperately trying to protect her son from destruction at the hands of a blackmailer, might be a distinct change of pace for the Scottish actress: based on a 1940s suspense novel by Elizabeth Holding (previously filmed by Max Ophuls as “The Reckless Moment” in 1949, starring Joan Bennett and James Mason), it’s quite direct and accessible. Swinton, of course, is best-known for her long collaboration with the late Derek Jarman, whose films were highly idiosyncratic and personal, and her other pictures, such as Sally Potter’s extravagantly offbeat “Orlando” and Tim Roth’s lacerating “The War Zone,” were definitely outside the Hollywood mainstream. Even Danny Boyle’s “The Beach,” in which she played against Leonardo DiCaprio, was an atypical studio product.

In a recent Dallas interview, however, Swinton saw her turn in the sophomore feature of writer-directors Scott McGehee and David Siegel (whose debut film was the defiantly enigmatic “Suture” in 1993), as eminently in line with her earlier work. “It feels very familiar to me–the fact that we end up in this fairly old-fashioned thing I find very modern, and rather radical, actually. It feels like the natural next step for me. It feels to me like…it’s linked up to at least the previous two projects, i.e., ‘The Beach’ and ‘The War Zone,’ in terms of being another look at mothers and what they do–what we do–and the whole question of controlling one’s family,” she said. (As the mother of twins, Swinton is more than a little familiar with the subject.)

She amplified on the point when asked about the highly inward, almost repressed nature of the woman she plays in the picture. “That thing happens to be the thing that I’m interested in. It happens to be my shtick,” she explained. “I’ve just been very, very lucky in that I’ve been given all sorts of opportunities, previously through my work with Derek Jarman for eight years–that was an extraordinary stroke of luck–because the things that we cooked up together gave me the opportunity to develop a real interest in exactly the kind of thing I’m interested in seeing in cinema–which is human behavior, and people thinking, and real acting. And this opportunity presented itself in exactly the same way. That’s what I mean when I say that it felt like business as usual to me–the very fact that she [Hall] is alone so much of the time…. The job is not to present an actor performing in concert with other actors, a person communicating with other people, but a performance that is isolated, so that the performer actually communicates only with the camera. That’s what I’m interested in. It has to do with being unwatched–that’s the experiment I’m interested in. How do you actually perform being unwatched? It’s an ongoing interest. I haven’t cracked it yet, but I’m continuing to be interested in it.”

Swinton also appreciated the centrality of her character in the narrative–despite the pressure it put on her for the success of the venture–because it allowed her to immerse herself in the project so fully and build her performance carefully and methodically. “One can identify oneself so strongly with the work, and also the calibration of your work can be quite precise,” she explained. She admires actors who make deep impressions in brief appearances–“you have to layer everything in just one scene,” she noted–but embraces the demands of a large, central role like Margaret: “If you’re in every scene, you can work much slower and much more precisely about different shades. It’s like a painting…. I much prefer it, and anyway I like pressure.”

Swinton’s acceptance of her role in “The Deep End” began with the script–which she called “the best-written script that I’ve ever worked with”–but its excellence wasn’t enough. “A script can only ever do so much,” she said. “Most of the filmmakers I’ve worked with have been terrible writers. But most filmmakers that I’m interested in–apart from the fact that they’re usually painters–are dealing in a kind of cinema that is primarily visual-based and much less literary. I don’t look for the part. I look for the people. I will read the material, [but] you meet them [the filmmakers], and then you know whether you want to be around them, whether you can work together. It’s the people, really.” And ultimately that’s what persuaded her to join McGehee and Siegel in making “The Deep End.” “When I met them,” she recalled, “it became very clear to me that we would be able to have a dialogue together, become fellow-travelers, as it were. And when I saw ‘Suture,’ it just confirmed it.”

She also praised the choice of the Lake Tahoe area as the perfect locale for the story about plots and emotions running far beneath the veneer of normal family life. It “was such a good idea,” she opined, “because that lake is so deep, and therefore the surface tension is so sinister in a way because of the clarity and the keenness. It’s a very, very beautiful setting for the story.” And, one might add, for Swinton’s performance in it–a performance which is an equally stunning combination of surface brilliance and emotional depth.

“The Deep End,” a Fox Searchlight Pictures release, will be opening across the country during August.