'I hope the film might encourage people to communicate with the ones they love,' Vanderbilt, 92, tells EW.

By Joe McGovern
March 18, 2016 at 03:28 PM EDT

Gloria Vanderbilt has been in the public eye for longer than practically anyone in the world. The heiress, artist, designer, philanthropist and beloved raconteur is now 92 years old — though you’d hardly think so from looking at or listening to her. That’s a point made by her fourth and youngest son, CNN journalist Anderson Cooper, in the documentary Nothing Left Unsaid: Gloria Vanderbilt and Anderson Cooper. Watch the exclusive trailer for the new film, above.

“She has this drive,” Cooper says in the trailer, “and that drive makes it impossible to have a calm existence.”

As chronicled with care and imagination in the new HBO film by Oscar-nominated director Liz Garbus (What Happened, Miss Simone?), Vanderbilt was born into one of America’s richest and most powerful families. In 1934, at the age of 10, she was the subject of a highly publicized child custody trial, and she later went on to gain much attention for her modeling and acting — and her affairs (with Frank Sinatra, among others) and four marriages. Her husbands included Fantastia composer Leopold Stokowski (he was 63; she was 20), famed director Sidney Lumet, and writer Wyatt Cooper, father of Anderson.

“Me and my dad, we always used to go down to see his family in Mississippi,” Cooper tells EW. “So I felt more connection there, much more to the Cooper side than the Vanderbilt side.”

The documentary, which features sparkling archival footage as well as many contemporary scenes of mother and son in lively conversation, is an attempt by Cooper to explore his Vanderbilt side — via his mother’s extraordinary life — and to ask his mother anything he’s ever wanted to know, including about the tragedies of her life. (The film reaches a haunting apotheosis in its last third, which focuses on the 1988 suicide of Cooper’s older brother.)

Dredging up the past is not something that frightens Vanderbilt, though perhaps it once did. In fact, she wholeheartedly endorses the talking cure.

“I hope the film might encourage people to communicate with the ones they love,” she tells EW. “And to do it without getting too sidetracked by anger or fear, but to really feel safe and open so that you’re not blocked. I think that may take time and age, but the sooner you can do it the better. It’s life changing and changes the way you see the world.”

Nothing Left Unsaid: Gloria Vanderbilt and Anderson Cooper premieres on HBO on April 9. (It also will air on Cooper’s home turf, CNN, on April 29.) And Vanderbilt and Cooper have a book of epistolary emails, called The Rainbow Comes and Goes, which is being released by HarperCollins on April 5.