The Christchurch massacre and the rise of right-wing extremism.

"Grafton is a monochrome, traditional, beautiful little country town. We now have... the distinction of having given the world a gentleman who's turned out to be Australia's worst mass murderer." Grafton resident.

The terror attack in the New Zealand city of Christchurch appalled the world. The indiscriminate shooting of 50 Muslim worshippers during Friday prayers was calculated to spread fear and a message of right-wing terror.

"My feeling is that he chose New Zealand because it was a soft target in terms of security and perhaps, he chose it to illustrate that even a relatively tolerant quiet society on the very edge of the world was not immune to terrorism." Far-right extremism researcher.

On Monday, Four Corners investigates how the Australian born accused killer was able to operate under the radar.

"They go to these forums where they can talk about this stuff safely. No-one knows who they are... They can talk about that far right violent extremism there, where they can talk about hating and, and killing." Former right-wing extremist.

The plot was intricately planned, harnessing the tools and the power of the internet, to amplify the terror to a global audience.

"He's made it clear by his own recording that he was driven by hatred of Muslims and by racist ideas, and he identifies as a white supremacist, although he may not be able to spell those words, but they're the kind of cultural values that he's tied himself." Grafton resident.

The attack brought to light the violent and disturbing right-wing extremist movement that is flourishing on the internet and finding a home in both New Zealand and Australia.

"I guess people don't realise, there's all these far-right groups out there." Former right-wing extremist.

The program investigates whether authorities have been so focused on Islamic extremism that they've failed to grasp another deadly threat, the rise of far-right white supremacists.

"I'm aware that intelligence agencies have been monitoring these groups, but my concern is that what they've done is that they've tended to focus on Islamic terrorism at the expense of really paying enough attention to the extreme right." Extremist researcher.

Under the radar, reported by Sean Rubinsztein-Dunlop.

Interference, reported by Nick McKenzie.

New evidence of China's covert political influence campaign in Australia.

"We've had multiple briefings at the top-secret level from ASIO and other agencies that foreign interference is being conducted in Australia at an unprecedented level." Federal Intelligence and Security Committee member.

In 2017, Four Corners, in a joint investigation with The Age and Sydney Morning Herald, revealed the lengths the Chinese Communist Party was going to, to influence Australia's politicians. In response, the federal government passed new laws to ban foreign interference.

"Political systems and parties just took what they could for as long as they could get away with it." Former prime ministerial adviser.

Now, in a new investigation, the joint reporting team can reveal fresh and compelling evidence of covert Beijing-backed political activity taking place in Australia.

"Chinese foreign policy is now following a much more assertive and, in some cases, aggressive approach." China analyst.

The investigation has uncovered secret information gathering operations targeting sensitive Australian intelligence analysis. And despite the new laws, there is evidence that Australian politicians have not listened to the warnings issued by Australia's own intelligence agencies.

"The Chinese Communist Party has sought to use all sorts of vehicles to have non-transparent mechanisms, means of influencing the politics in Australia and elsewhere." Former prime ministerial adviser.

Politicians are not the only ones receiving Beijing's attention. The investigation will reveal how Chinese authorities are stifling dissenting voices by targeting members of the Chinese-Australian community who fail to toe the party line.

"There is always a red line that everyone is actually quite afraid of crossing...because of repercussions from the Chinese consulate or the Chinese government." Newspaper publisher.