Updated May 15, 2003 12:57 PM

Handsome leading man Robert Stack, one of Hollywood’s best embodiments of the strong, silent type, died Wednesday at his Los Angeles home.

The star — whose film career started in the late 1930s but is best remembered for his role on TV’s classic ’60s crime drama “The Untouchables” and later “Unsolved Mysteries” — was 84.

His wife of nearly 50 years, Rosemarie, tells the Associated Press that Stack was found slumped over in their home at about 5 p.m. The actor underwent radiation treatment for prostate cancer in October, but his wife says he died of heart failure.

“He was feeling so good,” she told AP. “He had a bout with a tumor but that was gone. It wasn’t that. It was his heart. He was too weak. He wouldn’t have lived through a bypass.”

Stack’s film career began in 1939 with “First Love,” in which he gave famed young soprano Deanna Durbin her first screen kiss. He also went on to star in one of Hollywood’s best anti-war films, 1942’s “To Be or Not to Be” (as the handsome pilot who wooed Carole Lombard) and the first 3-D movie, 1952’s “Bwana Devil.”

But for many, he will always be remembered for his Emmy-winning role as the 1920s Chicago crimebuster Eliot Ness — based on a real-life character — on “The Untouchables,” which ran from 1959-63.

Stack’s deep voice and strong presence served him well in both drama (“Written on the Wind,” which earned him an Oscar nomination) and comedy (straight-faced and hilarious in “Airplane!” — a parody of “The High and the Mighty,” a 1954 John Wayne aviation melodrama that Stack also starred in).

He later became a familiar crimebuster to a new generation of TV viewers as host of NBC’s “Unsolved Mysteries,” and he remained a well-known and well-liked pillar of the Hollywood community, thanks to a winning combination of good looks, which never faded, and a chipper sense of humor.

“I think there’s a definite carry-over from Eliot Ness,” he told AP in 1998. “Somebody once said, ‘You really think you’re Eliot Ness.’ No, I don’t think I’m Ness, but I sure as hell know I’m not Al Capone.”