As we mark the 23rd anniversary of the September 11 terrorist attacks that shocked the world and changed the course of history, there are many stories of courage, faith and hope that bring light out of the darkness.

One extraordinary survival story features what many believe to be an angel, and a dramatic conversion to Christ while holding on to life after being buried beneath the ruins of the North Tower.

Genelle Guzman-McMillan worked on the 64th floor of the building. As she arrived at work that morning, she had no idea her life was about to be turned upside down, as she details in her memoir, Angel in the Rubble: The Miraculous Rescue of 9/11's Last Survivor [Howard Press].

When the building shook after the plane hit, colleagues were confused, and unsure about whether to leave. By the time they set off down the stairs, it was too late to escape the building's collapse.

"Brutal, diabolical, painful, vicious," wrote Genelle in her memoir. "Those are some of the words I've used to attempt to depict the hell of being hammered into the ground by more than ninety floors of a free-falling building. But no word will ever be sufficient.

"I knew death was inevitable—possibly in days, probably in hours, maybe even in minutes. The time was uncertain, but there was no doubt I was in for a slow, painful, isolated demise."

Genelle found herself pinned down by concrete, struggling to breathe, in intense pain. The expectation of approaching death led to some serious thinking about her life and the realisation of some painful regrets.

First was her daughter, Kimberley, who she had left in Trinidad over a year before in order to pursue her dreams of being a dancer and singer in the "glitz and glamour" of New York. As she lay entombed in the dark, she started to realise the harm this decision had caused. She also became convicted about her party lifestyle and other actions she perceived to be selfish.

She started to pray to a God she had paid little attention to in her adult life despite a Christian upbringing. She told him how sorry she was for all the bad things she had done. She promised that if she got out of this situation, she would work to put things right in her life.

"I was very sincere about every word," her memoir records. "I wasn't trying to fool myself or Him. And I wasn't trying to bargain with Him. I honestly felt the repentance in my heart."

Genelle heard noises which gave some hope. But it was towards the end of her ordeal, as her despair peaked, that something extraordinary happened. A hand reached down to hold hers, and a male voice said: "I've got you, Genelle. My name is Paul, and you're going to be okay. They're going to get you out soon."

It was only later, after trying and failing to find "Paul" to thank him for his help, that it struck her: how did he know her name? She now believes that it was an angel sent to help her through the final tortuous hours.

Her physical rescuers told her later that they didn't see any "Paul". Instead, they had first found the body of a deceased fireman – which then led them to Genelle, who would become the last person to be rescued alive from the wreckage. It took hours to free her from the concrete, and she was rushed straight to hospital, to the delight of her friends and family who had thought that she must be dead.

Recovery was a long process but her new faith helped her to cope and she drew spiritual lessons from her experience. She was baptised, she married the man who had been her live-in boyfriend, her daughter came to live with her in the US, and she began to serve and worship at her new church.

It might seem to be a miracle that anyone could possibly have survived the collapse of an enormous building on top of them. Two others who survived, the police officers Will Jimeno and John McLoughlin, had their stories immortalised in the 2006 Oliver Stone film World Trade Center.

"How on earth did I survive being crushed by one of the most massive structures on the planet? How did I last as long as I did in those conditions?" Genelle asked in her memoir.

"It was all God. He had a plan for me—one I could neither explain nor take an ounce of credit for. But I firmly believe that the first of countless steps in His plan for me was to draw me near to Him. I apologized, and He accepted. I promised, and He believed.

"It didn't feel like only concrete and beams had been lifted off me, but a dark veil that had been shrouding me for years as well. It was a wonderful, magical feeling to know that the best story I was going to have to tell from my tribulation to my family and friends was that, when it was over, I had made a new best friend, one I could count on for anything and one I would spend the rest of my life serving with honour and glory."

Heather Tomlinson is a freelance writer. You can find her work at https://heathertomlinson.substack.com/ and on X @heathertomli