Every day the British actor passed a homeless couple outside his New York apartment block, often stopping to spare some change.
And then one day, they were gone. Bettany dedicates Shelter, which received its second-ever screening at the Dubai International Film Festival on Friday, to this unnamed, unknown pair.
"I passed this couple every day when I was taking the kids to school," says the 43-year-old star of A Beautiful Mind and Wimbledon.
“Slowly they became more and more invisible to me, more and more part of the landscape of the city,” he says. “Then Hurricane Sandy happened. I got my family out, and when we came back, I never saw them again.”
Left to wonder what fate the pair faced, Bettany poured his feelings into a raw, unnerving depiction of a homeless couple on the same city’s streets.
“I would give them money, pass them, and that was all,” says Bettany. “This film is, in some way, a response to the guilt I experienced having not crossed that boundary.”
It's clearly a highly personal project – as well as writing, directing and co-producing Shelter, Bettany cast his wife Jennifer Connelly as the female lead. Hannah is a homeless heroin addict who finds first support, and then later love, alongside Tahir (Anthony Mackie), a Nigerian immigrant who has outstayed his visa.
Meticulously researched and realised, Bettany spent months meeting homeless people in shelters, and reached out to New York’s Coalition for the Homeless to check the script for authenticity.
The couple's story is one of survival and, at times, hope. But Shelter is not easy viewing. Connelly features in a number of uncomfortable scenes, which depict grotesque sexual acts and graphic drug use; it was the first time Bettany had to direct his partner, who he married 11 years ago after they met on the 2001 set of A Beautiful Mind.
“I think there was an incredible amount of trust between us,” he says. “The decision to trust me for 21 days of filming is probably tiny compared with the amount of trust she needed to spend a life with me.”
Connelly's performance, as a widowed middle-class woman who turns to drugs for escape, is mesmerising. However it's easy to make comparisons between Shelter and the American actress's celebrated role as an addict in Darren Aronofsky's 2000 indie hit Requiem for a Dream.
"Darren tends to make movies about obsession," says Bettany. "I know he would tell you that Requiem for a Dream wasn't a film about addiction, it was a film about obsession. And I had no interest in making a polemic about drug addiction being bad, or homelessness being bad, because every decent human being knows that it is – the film is about judgement."
True judgement, arguably, necessarily comes from the divine. While Bettany states he is not a believer, religion is a major theme in the movie. Islam offers Tahir a respite – a “place for quiet and peace” in place of Hannah’s reliance on drugs. The movie’s morality was informed by Bettany’s own Catholic upbringing.
“Whenever my father saw homeless people he would say: ‘There but for the grace of God go I,’ ” recalls Bettany.
“I really miss that sentiment – it’s an acknowledgement of how close all of us are to having made bad decisions in our life, or ending up in the same predicament.
“We are all of us innocents, and we are all of us worthy of forgiveness – and we are all absolutely fundamentally worthy of a home.”
• Shelter screens on Sunday, December 14, at 3pm at Mall of the Emirates 8. For more information, visit www.dubaifilmfest.com