Half a century after they first starred opposite each other, screen legends Jane Fonda and Robert Redford have teamed up again in a poignant tale of love, loneliness and companionship in later life.

"Our Souls at Night" had its world premiere Friday at the Venice film festival, where the veteran stars were to be presented later with Golden Lions in recognition of two of the longest and most successful careers in US cinema.

Based on a Kent Haruf novel, the Netflix production sees Indian director Ritesh Batra delve into a world of creaking bones and reading lights that is increasingly a focus for a film industry chasing the disposable income of retired baby boomers.

Fonda and Redford play Addie Moore and Louis Waters, a pair of retired, widowed neighbors living quiet lives in small-town Colorado. They have known each other for years, but never really known each other. That changes when, on the instigation of Addie, they begin sharing a bed -- on the basis that company and conversation will help Addie's insomnia and ease the loneliness they both feel most acutely after dark.

As the friendship develops, the nighttime chat becomes more serious. It emerges Addie and Louis share lingering regrets over how they handled traumatic moments in their married lives and consequent strains in their relationships with their adult children.

The bond between the two deepens when Addie's seven-year-old grandson comes to stay with her while his newly-single father struggles to keep his life on track. Soon the question of what kind of relationship they are having, and where it is headed, becomes more pressing.

The film is Batra's third feature, after 2016's "A Sense of an Ending" and his award-winning 2013 debut, "Lunchbox."

The director was born in the same year that Redford, now 81, and Fonda, 79, released their last film together, Sydney Pollack's 1979 western, "The Electric Horseman," in which they play a romantically-entangled rodeo rider and a reporter.

Prior to that, the pair played young married couples in 1966's "The Chase" and the following year's "Barefoot in the Park."

On all three of the films, Fonda fell for her famously handsome co-star, she told an interviewer earlier this year, quipping that it was a sign she had finally grown up that she had not gone weak at the knees this time around.

Also showing in Venice, and tipped as a potential contender for the Golden Lion, is "The Leisure Seeker", which sees Helen Mirren and Donald Sutherland play a free-spirited older couple who embark on a Boston-Florida road trip to get away from their doctors and bossy grown-up children.

The issue of loneliness after bereavement also provides the backdrop to "Victoria & Abdul," Stephen Frears's handling of the true story of the elderly Queen Victoria's friendship with an Indian clerk.

"Our Souls at Night", which was shown out of competition here, will be released by Netflix on September 29.