"Assassination Tango," the new thriller about a hit man with a taste for dancing, is a Robert Duvall movie in three different ways.
For one, this most gifted of actors plays the main character, an American assassin named John J. who's been hired by politically vengeful Argentines to murder an aging general. Mr. Duvall brilliantly portrays him as a mercurial mixture of gentleness and malevolence. For another, Duvall wrote the screenplay, bringing to bear his view that human nature is more complex and unpredictable than most Hollywood movies acknowledge.
Most important, Duvall directed the picture. As in the previous fiction films he's directed, "The Apostle" and "Angelo, My Love," he refuses to draw solid boundaries between the calculated acting of trained performers and the spontaneous behavior of everyday people. This explains his decision to use his longtime girlfriend Luciana Pedraza - a professional tango dancer, not a conventionally schooled actress - in a central role.
The willingness to blend professionals and nonprofessionals is Duvall's most interesting directorial trademark. Most commercial filmmakers hesitate to use this technique, but he doesn't see it as risky.
"When you're dealing with a specific culture," he told me at last fall's Toronto Film Festival, "you can find people who are terrific natural actors. They know the subject, and often they're so pure they put the professional actors on notice.... I don't coach them, I just give them their space. There's no burden of getting a particular result. It's the process that's important."
When it succeeds, this approach gives Duvall's movies rare overtones of authenticity. The evangelical community he portrays in "The Apostle" and the gypsy characters of "Angelo, My Love" are as believable as the people found in regular documentaries, and this lends extra credibility to the fictional stories that frame them.
"Assassination Tango" offers a good testing ground for Duvall's unusual methods. Dancing is at the heart of the film, and who can present a more graceful, sensuous tango than Argentines who've lived and breathed it all their lives? Settings, costumes, and music also convey the aura of an environment that's as genuine as it is exotic.
The weak link is Ms. Pedraza's performance as the dancer who teaches the tango to John J. She is a superb dancer, but she doesn't have the talent needed for nonmusical scenes. This crimps the movie's effectiveness, since "Tango" is as much a romantic story as a suspense thriller and dance extravaganza. Duvall's latest is a treat for the eyes and ears, but it doesn't always ring true on deeper dramatic levels.
• Rated R; contains violence and vulgar language.