With the Winter Olympics just days away, North and South Korean athletes are preparing to march side by side in Seoul, but the smiles, handshakes and blue and white unity flag mask the ongoing tensions between the two nations.

The last time the Olympics took place on Korean soil, the two nations’ decades-long dispute resulted in the loss of 115 innocent lives.

It’s something that Kim Hyon-Hui would like to forget, but as Olympic rings go up across Seoul and advertisements with news of the athletes’ imminent arrival blare from TV screens, that’s becoming more difficult than ever.

Now the 57-year-old housewife leads a seemingly ordinary life in South Korea’s third largest city. She enjoys attending church, hiking and raising her two teenage sons.

Kim Hyon-Hui was 19 years old when she began her training at the North Korean Army’s secret, elite espionage school. (ABC News)

But in 1988, she was watching the Seoul Summer Olympics from inside a South Korean jail cell, charged with blowing up a Korean Air flight and fully expecting to be put to death for her crime.

The plane went down en route to Abu Dhabi, killing everyone on board.

When she placed the bomb – disguised as a Panasonic radio and hidden in a shopping bag – in the overhead compartment of the plane and then got off the plane in Abu Dhabi, she wasn’t thinking about the lives she was about to destroy.

The plot, she told the Washington Post , was simply a “technical operation”.

Ms Kim had been training at the North Korean Army’s secret, elite espionage school since she was a teenager. By 25, she was a well-oiled machine of the North Korean regime, trained to kill with everything from her hands and feet to grenades and assault rifles.

Then, one day, she was chauffeured to a foreign intelligence building with an older male spy who was to pose as her Japanese father and given their mission: to down a South Korean passenger plane.

When she was captured, it took weeks for South Korean interrogators to obtain her confession. (AAP)

North Korea had tried to co-host the Olympic Games but when negotiations fell apart, they instead turned to trying to stop the Games from proceeding at all.

“By destroying this plane, we intend to increase this sense of chaos and ultimately prevent the Olympic Games from taking place in Seoul,” an intelligence director told young Kim, she wrote in her 1991 book.

The note describing her mission was handwritten by Kim Jong-Il, dictator Kim Il-Sung’s son and successor as ruler.

After being given their mission, the pair travelled across Europe posing as Japanese tourists before collecting the bomb from two other agents in Belgrade.

They flew to Baghdad with the weapon, where Kim activated the timer and boarded Korean Air Flight 858.

The two agents got off the plane in Abu Dhadi. Several hours later, the bomb went off over the Indian Ocean. There were no survivors.

Authorities caught up with the pair in Bahrain, alerted by their convoluted travel plans.

When they realised they’d been caught, both spies bit down on cyanide-tipped cigarettes provided by the North Korean intelligence agency – following their instructions to kill themselves rather than reveal information.

Authorities wait as Ms Kim disembarks in South Korea for the first time, following her capture. (AAP)

The former spy says North Korea's leader at the time, Kim Il-sung, was treated as a god. (AAP)

The older spy died, but Ms Kim survived. When she woke up, she was handcuffed to a hospital bed, an oxygen tube in her nose and surrounded by men in combat fatigues holding machineguns at the ready.

According to South Korean investigators, it was weeks before her barriers began to break down and she began to confess to taking part in the plot.

It took a sightseeing tour around Seoul by South Korean special agents – where she saw families smiling, shopping and buying food from street stalls – for her to begin thinking that her mission had been a sham.

“Founded upon lies,” she told the Washington Post.

She began to talk.

Months later, she watched the Opening Ceremony of the Seoul Olympics on television from inside prison.

“I still remember the theme song they played,” she said.

“Everybody seemed joyous. I was thinking to myself, ‘Why did North Korea do this?’”

North Korea continues to operate its network of spies and special agents to this day. Most recently, they have been implicated in the murder of Kim Jong-un’s estranged half-brother, Kim Jong-nam, in Kuala Lumper in February last year.

But the downing of the Korea Air Flight 858 remains the hermit kingdom’s deadliest terror attack – and the act which prompted the United States to list North Korea as a state sponsor of terror.

Since her release, Ms Kim has worked to atone for her actions. Here, she is pictured meeting with the son and brother of Yaeko Taguchi, a Japanese woman abducted by North Korea in 1978. (AAP)

In 2017, North Korea was reclassified as a terrorist state.

Ms Kim was given the death sentence by a South Korean judge but in 1989 South Korean President Roh Tae-woo pardoned her, saying she had been brainwashed and was merely used as a tool by the real criminals, North Korea’s ruling Kim family.

Now, Kim Hyon-Hui works tirelessly to atone for her actions.

She visits the families of Japanese people taken hostage by the North Korean regime. After being pardoned she wrote a book, Tears of My Soul, about her experiences as a North Korean spy, with the profits donated to family members of the Korea Air Flight 858 victims.

“Can my sins be pardoned?” she asks.