In 1942, Marcel Heuzé, a French tool worker, was deported to Germany to work in a Nazi labour camp.
Over the next two years, Heuzé sent dozens of letters to his wife and three daughters back home in France.
Because of strict German censorship, many of those letters never arrived.
In 2002, almost 70 years later, Carolyn Porter purchased five of those undelivered letters from an antiques dealer in Stillwater, Minnesota.
Unable to read French, but able to recognize "they were written with care," Porter decided to have the letters translated in 2011.
"Time seems to go so slowly without you and without my girls," Heuzé wrote in one of his letters. "All the letters I receive tell me that I'm awaited with impatience and it makes me sad."
"Once I had the first letter translated, the story started unfolding and I had to read the rest. It was so beautiful and heartbreaking," Porter, 43, told the Daily Telegraph.
"When I had finished, I just wanted to know whether he had lived, whether this man returned to the wife and daughters he loved so much. I knew it was unlikely given the horrible things he described, but I was hoping, hoping for a happy ending."
Porter worked with a genealogist for a year and eventually tracked down Heuzé's family.
"The day they told me that Marcel had lived to return home to his family, I started bawling as I thought it was so unlikely," she said.
While Heuzé and his wife are no longer alive, they died 20 and 7 years ago respectively, their three children were eager to received the long-lost letters. Porter told the Huffington Post that she sent Heuzé's grandchildren and great-grandchildren copies of the letters.
At the news of his father's recovered letters, Marcel Heuzé Jr., 63, who was born after the war, told the Telegraph, "I almost fell off my perch."
Heuzé Jr. believes the letters were censored by the Germans as one was "stamped with a swastika," and then taken back to the US and eventually sold by a serviceman after the war.
Tiffanie Raux, 24, Heuzé's great granddaughter, said she and her family couldn't thank Porter enough for her "altruistic" gesture.
"It's very American. I'm not sure people in France would have gone to all that trouble," she told the Telegraph.
"It's been a few months since the first five letters were shared with the family, and honestly, I still get emotional when I think about it," Porter wrote in an email to Yahoo.
Porter will be visiting Heuzé's children in Paris in two weeks with another collection of letters, ones that she tracked down in California.