LOS ANGELES -- Christopher Plummer may be frozen in some filmgoers' memories as the noble-browed patriarch who made stern parenting and anti-Nazism sexy in "The Sound of Music."
But Plummer and his career aren't mired in the past. He's created Leo Tolstoy in "The Last Station," the haunted magnate in "The Girl With the Dragon Tattoo" and a man experiencing a late-in-life gay awakening in "Beginners," which earned him an Oscar last year at age 82.
That made him the oldest acting honoree ever, and he's not stopping. He plays a U.S. Supreme Court justice in HBO's "Muhammad Ali's Greatest Fight," debuting Saturday (8 p.m. EDT), a history-textured film that puts the boxer's quest to be recognized as a conscientious objector against Vietnam War service and the high court in the ring.
"I don't think retirement exists in our profession," said Plummer, looking every bit the star in elegant slacks and jacket, his white hair perfectly groomed. "If you retire, something's gone very wrong with your career is my theory. Also, why would you want to retire? It's fun to be in this weird, old, ancient, ancient profession."
The Canadian-born Plummer heads the HBO film as John Harlan II, who was among the justices who decided in 1971 whether Ali's conviction for refusing to be drafted because of his Muslim-based objections should be upheld or overturned.
Stephen Frears, an Oscar nominee for "The Queen," directed, and the script is by Shawn Slovo ("A World Apart"). The film is based on the book of the same name by Howard Bingham and Max Wallace, with additional research by Slovo.
The story resonated with Plummer because of Ali's anti-war stance and Harlan's intellectual metamorphosis.
His law clerk, a composite character played by Benjamin Walker ("Abraham Lincoln: Vampire Hunter"), persuades him to take a second look at the case.
"One man, because he listened to somebody else, was intelligent and vulnerable enough to change his beliefs," Plummer said.
The cast members, mostly stage-trained actors including Fritz Weaver as Justice Hugo Black, were a joy, Plummer said: "We did feel like a club, the old boys' club."
Also a boon was the chance to work with Frears. He compared him to another famed filmmaker, John Huston.
"Both those directors are so great because they give you such confidence. They're with you, they're a pal. That's what a really fine director is," Plummer said. "Not somebody who gets busy and says, 'Maybe we should try it this way, or this way.'"
Although Plummer is part of a very exclusive club whose members each have won Oscar, Emmy and Tony awards, he declines to pick out his most satisfying performance.
"None of them," he responds quickly. "I always feel I can be a hundred times better."
Even in the case of an Oscar-winning role?
"Yes, of course, God, yes," Plummer said. "I can go on forever talking about other people's films. But not necessarily mine."