Truong and his American partner Mark Newton were arrested and charged in February 2012 over their involvement in a child exploitation conspiracy involving their then six-year-old son.

During proffer sessions with police, Casper revealed he was a member of a secret internet relay chat group called Tail of the Dragon and began providing inspectors with several names behind the aliases.

The key that unlocked the conspiracy and led to the discovery of Adam was a visual clue contained in a private folder of another Tail of the Dragon member, 44-year-old Thomas Vaughn in Anderson, Indiana.

Tail of the Dragon remained undetected for almost 20 years.

Protected by walls of encryption and security software, members of the group assiduously worked to thwart law enforcement and evade detention, switching internet channels frequently, changing aliases and chat room names.

All had concealed their identities using multiple screen names and aliases.

There was an Australian in the group, an early member using the alias Red Rover. Logs from the chat room seen by Four Corners reveal Truong was an active member up until he acquired a child of his own, Adam, in 2005.

We're working on a case now that will bring down a network, but it takes time, dedication, and it takes that network, that global reach that we've managed to maintain now for 13 years, to make those things happen."In the months before Truong and Newton left their Cairns home for another extended international holiday with their adopted son Adam in 2011, at least two key figures in their global network had been arrested by police and charged with child sex offences.

But the conspiracy involving Truong and Newton was yet to be uncovered.

Inspector Bone discovered a spindle of DVDs hidden in a crawlspace inside Casper's home, showing Casper abusing multiple children.