The odd death of Kim Jong-nam, the estranged half-brother of North Korea's leader Kim Jong-un, has focused a spotlight on the secretive country. But that light isn't revealing much for journalists trying to investigate what happened.  

"North Korea is possibly the most difficult place on earth to get information out of. The curtain is very tightly drawn at all times," says Saša Petricic. 

Watch the full The Investigators episode at the end of the article.

CBC's Asia correspondent has been reporting on Kim Jong-nam's death, and the subsequent murder investigation by Malaysian police, by pulling together information from other countries to try to figure out what happened, an unfamiliar experience for journalists accustomed to going to the heart of a story to report on it.

"You have to piece together these bits and pieces of information, and try to come up with a broader narrative," he says.

Petricic has been to South Korea, but that's as close as he got to the so-called "hermit kingdom," adding "the average North Korean probably knows very little, if anything, about this case," in spite of the fact it's been making headlines around the world.

While CBC journalists have been to North Korea in the past, those visits are tightly controlled and usually at the invitation of the ruling party when there's something it wants Western media to see — unlike now.

"They've been holding news conferences," Petricic says of North Korean authorities who've responded to the worldwide attention on the story. "But not inside the country, not in North Korea."

The Investigators with Diana Swain - Covering North Korea and the killing of Kim Jong-nam22:20

Kim died en route to hospital last month after being attacked by two women as he stood in line at Malaysia's Kuala Lumpur International Airport. The incident was caught on overhead security cameras and appears to show the two women smearing Kim's mouth with a rag that Malaysian authorities believe was coated with deadly VX nerve agent, a banned chemical weapon.

The two women were this week charged with his murder, widely speculated to have been ordered by his estranged half-brother.

While Western news agencies such as the Associated Press or Agence France-Presse have bureaus in Pyongyang, their work is monitored and restricted by North Korea's communist government.

Undercover in North Korea

That's why journalist Suki Kim says she took the extraordinary risk of sneaking in.

In 2011, she got a job at a university, teaching the children of North Korea's elite families. But during her six months in the country, she was secretly taking notes for a book that she wrote when she left.

"I came out of there with about 400 pages of notes. And because my cover was a teacher, I could have a laptop with me, which I carried with me at all times. I wrote morning and night, and kept all the documents on USB sticks, and erased everything from computer every single time. I kept an SD card, where I had a backup copy — which I also hid."

Kim has little doubt what would have happened had she been found out.

"To actually write a book in there has never been done — because it's that scary. It's a country where they send people to gulags [prison camps] for, you know, carrying a Bible and passing it out," she says. "So I don't think that what I had done would have let me live, really. That's my guess. And that fear was there all the time. Every second.

"There was just no other way to tell the truth from inside North Korea."