A new RTÉ documentary, "Girl from the Letter", tells the fascinating story of a 74-year-old man who tracked down his long-lost sister. 

The RTÉ radio documentary "Girl from the Letter" follows Cork native John Richards as he embarks on a quest to locate the sister that he never met. 

John's father John Joseph Alfred Richards abandoned his family when John was just four years old and that was the last John heard of him for over 20 years. 

John's mother Sheila gave him very few details about his father, stating only that he was born in Wales and grew up in Ireland. He was on a trip to England in the early 1950s when he vanished. 

Sheila raised John and his brother Donal as a single mother in the 1950s and 1960s before a letter arrived from John Sr. in the early 1970s asking if he could return home.

John - now aged 25 - met his father for the first time in more than 20 years right before his marriage to his wife, Nell. 

However, just 18 months after he reappeared, John Sr. received a letter from a young girl warning him that she would be sent to Ireland with a tag around her neck if he didn't return to England. He disappeared for a second time one week later, this time for good, leaving Sheila heartbroken. 

John's wife Nell said Sheila was left "heartbroken" by the second disappearance. 

"The life was gone out of her. She continued the same way she always did but she was deflated," Nell told the documentary. 

Sheila was diagnosed with cancer in the early 1980s and died aged 59. 

Following the death of his brother Donal in 2020, John decided to search for his half-sister who had penned the letter to his father almost 50 years ago. 

He joined forces with genealogist PJ Hogan and RTÉ producer Shauna McGreevey to search birth records, death records, and military archives and track down his missing sister. They also made use of DNA tests and Ancestry.com to aid their search. 

After numerous dead ends, Hogan unearthed John Sr.'s death certificate and discovered that John had not one, but five half-siblings.

John's son Keith made the initial contact, messaging a woman named Karen on Instagram. Finally, after 50 years of searching, John had located the mysterious sister who had written to his father all those years ago. 

John said he started crying within a minute of calling Karen for the first time. 

John and Karen have yet to meet up but plan to do so before Christmas. 

"I'm not blaming anybody. It's just life isn't it," Karen told the documentary. 

* "Girl From The Letter" is now available on the RTÉ Player or wherever you get your podcasts.