It was a single snapshot. A tattered flash of color amid acres of toxic grey ash and twisted steel that blanketed Ground Zero of New York’s twin towers on September 11, 2001.

A simple family photo, it showed a young woman smiling as she cradled a toddler in an embroidered red dress.

But to Australian photographer Nathan Edwards, it was a searing jolt of normal on a day when it seemed there would never be normal again.

He snapped a picture of it lying in the rubble, one of thousands of images he captured as he documented downtown New York after the World Trade Centre collapsed.

Much of what he saw in the coming days was unforgettable. The city and its people reeling, scrambling for answers, searching for survivors.

But there was something about that picture that clawed at him. Who were they? Did they survive? Were they among those who lost someone that day? Maybe a young dad who kept the photo on his desk?

He thought about it often. At times it became an obsession. When things were difficult in the years that followed — moving to a new town, an attempted career change — that’s when the mystery of the woman and the baby haunted him most.

He would wake sometimes with those questions turning in his mind and he knew it wouldn’t stop until he had answers.

“Just to find that picture in the rubble when everything else was ground to dust — I guess it felt like a bit of a sign,” Nathan said. “From the moment I found it, I wanted to know who the people were, and I really wanted them to be alive.”

Nathan remembers waking on that terrible Tuesday after spending 14 days straight covering 20-year-old Lleyton Hewitt winning the US Open. He planned to spend the day with wife Kylie doing what they loved most, wandering Manhattan, shopping, bar hopping and exploring.

“My boss called and said: ‘There has been a plane into the World Trade Centre and we need you to get down there’,” he said. “Just as I was leaving that second plane hit, so I said to my wife: ‘This is not an accident, and you probably won’t be able to contact me and you won’t see me. It could be for a couple of days’.

“I got there just as the second tower was coming down. It was a massive rumble and then it was just dead quiet.”

Then another noise started and it sounded continuously for the next few days.

“There was a beeping,” Nathan said. “I later learned that when firemen stop moving the little devices on their breathing apparatus beep. That’s them saying ‘I need help, come and get me’, and that was everywhere.

“You could hear them under there. But it was such a mess you would talk to firemen and they didn’t know where to start.”

There was nothing but grey dust and fear everywhere he looked that first day.

“It was towards the end of the day and something caught my eye, it was just lying there, this bit of color,” he said.

“There was some dust and I didn’t touch the photo, I just blew the dust off to show the faces and took a photo.

“I remember picking it up because I felt like I should keep it safe. I was thinking, ‘What do I do with it?’, when I ran into a firefighter and asked him. He said he was going to the place where things were being collected and took it from me.”

Nathan doesn’t know whether the snapshot is among tens of thousands of artefacts catalogued after 9/11, but efforts are being made to track it down.

“I remember leaving Ground Zero the first day and I walked back to my office in midtown and the further I got away from there the more normal life became,” he said.

“I remember walking past Macy’s (department store) and there were people walking out with their shopping, there were people eating in restaurants and having coffee.”

Punch drunk with exhaustion and adrenalin, Nathan wondered: “Don’t they know what’s happened?”

Nathan returned to Australia at the end of his secondment to the New York Post and settled back into life in Sydney, and later Port Macquarie on the New South Wales mid-north coast.

He and Kylie, 44, moved north after the births of their son Jack, 9, and daughter Olivia, 5, so they could be closer to family. Nathan dabbled in commercial photography before returning to his first love, news.

He continued to be haunted by the photo and on seminal anniversaries — one, five and 10 years — he cast the net wider. But there was nothing to show who the people were, whether they had survived.

Before the 10th anniversary in 2011, Nathan spent months tracking down the firemen who featured so heavily in his 9/11 portfolio, returning to meet them and tell their stories.

To a man, those guys love Nathan. Some hadn’t cried about their losses, but when confronted with his photos they broke down.

Nathan was also in touch with survivor groups whose members were increasingly connected through online communities. He regularly posted his photo on their sites.

In February last year he decided to give it one last shot in the lead up to the 15th anniversary and scatter gunned social media.

He’d had lines in the water for years but, for whatever reason, this time one of them gave a tug and by late that night his heart jolted as he found a solid lead through a member of a survivor’s network. After some not-so-gentle prodding, they offered up the name Jennifer Rothschild Robinson.

‘NO, NO IT CAN’T BE’

Stretched out on her hotel bed, Jennifer Robinson was five days into the first break she and her corporate lawyer husband Paul had taken since their baby Isabelle had arrived. By now they had found their holiday stride.

Gym junkie Paul had risen early to find a cross-fit class near their Cape Cod hotel. Jen, who only a week before had been so tired juggling full-time work as an insurance lawyer with new motherhood that she was falling asleep on the subway, was watching re-runs of MASH, waiting for him to return.

As he drove towards their resort, the air above suddenly screamed so loudly he pulled off the road. He was being buzzed by two F-15 jets and his first thought was that they looked like they were going to war.

He turned on the radio to hear news of the destruction wreaked on their beloved New York. His echoing thought: “Thank God Jen wasn’t at work.”

Paul walked into their room to see her smiling at a joke on the screen.

“I told her she needed to turn on the news and as she did we saw the second tower come down,” Paul said.

“My wife collapsed then. She fell to the ground and it was quite a long time before she could even understand what I was saying. She was just saying ‘no, no, it can’t be’.”

Jen’s office at Ohrenstein & Brown was on the 86th floor of the North Tower. Just seven floors above, five Al-Qaeda fanatics had crashed the hijacked American Airlines Flight 11.

She lost two colleagues that day, her dear friend AnnMarie Riccoboni, a grandmother and accountant, and office secretary Valerie Murray. The mention of AnnMarie’s name still makes her cry.

It’s not clear how her friends — and many others — perished. But almost half of the 2977 victims were from above her floor in the North Tower.

Many of those were the falling people, filmed plunging to their deaths after jumping to escape the horror and heat.

CALM IN THE STORM

Thinking back now, Jen, 50, and Paul, 49, remember not being quite sure what they should do next. In a daze they spent a strange afternoon with friends in nearby picturesque Provincetown. They still have photos showing them in unusually subdued tourist spots, no smiles on their faces.

Nathan’s photograph ran on page 12 of the New York Post the following day, and back at Jen and Paul’s upstate New York home the phone started ringing. Callers were hanging up lightning fast when Jen didn’t answer because their nanny Carmi was still minding Isabelle.

“People in New York, friends of mine, opened up the Post and saw this photo and knew it was me,” Jen said. “Some people were just hanging up when they heard Carmi’s voice. Eventually we told her just to answer the phone saying, ‘Jen’s OK, everything is fine’.”

In the years that followed, Nathan’s photo wove itself into the fabric of the Robinsons’ life. The page torn from the newspaper was stuck to the fridge to remind them of their remarkable good fortune, a talisman that told them not to be distracted by the small stuff.

It meant so much to them they wanted to find the photographer, partly to see if he took the same kind of meaning from his experience as they did.

They contacted the Post a few times, but in the chaos of that week very few photos were catalogued properly.

“Ever since that photograph came out and we started our search for the photographer it’s been a reminder both of how grateful we are that the outcome wasn’t different for us, and also an open question of who took it and what it meant to them,” Paul said.

“It remained in my drawer at work where I pulled it out whenever I had something that was particularly overwhelming. It put things right back in perspective.”

Over the years — with the arrival of another daughter Emma, now 11, and moving to Florida for Paul’s work - the image stayed with them.

Jen would post it every year on Facebook and give public thanks for her survival as well as pay tribute to her lost friends.

AT LAST, AN ANSWER

When Nathan began searching for Jennifer Rothschild Robinson on the internet, the photo he took in the rubble was one of the first things he saw on her Facebook feed.

Not only had mother and child survived, she had been looking for him too.

Nathan describes his initial reaction as “like being hit with a sledgehammer”.

He said: “I was thinking, ‘Maybe they don’t want to be found, maybe they have moved on with their lives and put all that behind them’.

“I sent the message late at night, midnight, and went to bed and got a response the minute I woke up. It was disbelief and then it was euphoria — I couldn’t believe I had finally made contact.”

That morning in the US, Jen’s computer pinged with a message. It was a photographer in Australia who had been searching for the woman and the baby in the photo.

“I felt so many things,” Jen said. “It just took my breath away. My heart was just up in my chest and I just couldn’t believe what was happening.

“I just went running up the stairs to Paul and I was crying and the first thing I said was: ‘Don’t worry, it’s OK’.”

 ‘I CAN’T BELIEVE I FOUND YOU’

Travelling from Sydney to Florida, Nathan, 44, is uncharacteristically jittery. He’s a laid back country-raised father-of-two with a strong line in laconic asides and, as he gets older, dodgy dad jokes.

Even he is surprised at how much he has invested in this search and now that he is actually going to meet Jen — an opportunity she and Paul leapt at when Nathan suggested it — he’s starting to fret.

“What if she doesn’t like me?” he asks at one particularly vulnerable moment.

He’s all nerves again on the morning of their meeting and the tension rises a couple of notches due to delays caused by the film crew we have with us.

Nathan’s pacing on the manicured street outside Jen’s Florida home waiting for things to get moving. Inside, Jen is all-American hospitality, offering coffee in any number of ways and bottled water, chatting to cover her nervousness.

When it’s finally time, Nathan walks towards her porch and knocks on the door behind which Jen is standing, clenching and unclenching her fists.

“Hello,” beams Jen.

“Hello, how are you?” Nathan says, bending down to wrap her in a bear hug that lifts her off her feet. “It’s so good to finally see you. I can’t believe I found you.”

Their sentences are spilling over each other and their nerves are gone as they try to put into words how much this meeting means, each of them tearing up.

The photo was taken when Jen took five-month-old Isabelle to her office the December before 9/11. She has kept the outfit Isabelle, now 16, was wearing and pulls it out with her snapshots.

“When I first saw it I imagined that it had sat on a desk somewhere,” Nathan said. “Everything that day, nothing had survived and to see a photograph that was relatively unscathed when everything around was just ground up dust - it just stopped me.

“There were several times over the past 14 years that I was telling myself maybe you will never find them. There were a few times when I said, ‘It has been so long, you’ve tried so hard, you probably need to just give up and move along’.

“But something wouldn’t let me give up. A little voice just kept saying ‘keep going’.”

A SOMBER RETURN

A few days after that first meeting we travel to New York to join the Robinson family on their first visit to the 9/11 memorial grounds.

Nathan is tetchy, but he settles when they arrive. He is genuinely touched at how this means so much to them as well.

Jen and Nathan drift along the North Tower memorial where victims’ names are carved in metal. They chance upon the names of her friends and hug again.

“I feel like I have a new friend,” Jen said. “Even though it’s only been a few days it feels like I have known him for a long time.

“I had never really thought of it before from his perspective. I had always wondered who is the photographer and thought how lucky I am, but it didn’t occur to me how much it meant to him.

“When we first met I was so anxious and excited and nervous and we hugged each other and I knew. I knew just how important it was to him.”

Paul says the experience of meeting Nathan had been “transformative” for Jen.

“It was sort of like an open wound,” Paul said. “I am watching Jen as Nathan has come over and I see this has shifted a piece that I think may enable her to actually put this whole experience in a good perspective.

“Watching the two of them, there is sort of a tacit kinship that you can see exists.

“Because it very well could have been whoever took the photograph didn’t care. And it could have been that we said: ‘Oh interesting, our photograph is in there (the paper)’.

“But the combination of his intensity in pursuing this and Jen’s attachment to the photograph and it’s meaning was incredibly special.”

That Jen and Nathan were both so invested in the search underscores the serendipity that skips so lightly through this story.

It is a tale of fateful linkages and chance. Of luck and despair. And of the power of a single image to inspire for almost 15 years.

But above all, it is special because it is a simple distillation of the power of hope.