The Cave of the Opal Eyed Snake is the first book in the Series, The Aussie Time Travellers.
Three Australian boys follow the sound of a didgeridoo and are enticed into a hidden cave containing ancient rock carvings. They are intrigued by the carving of a snake with an eye made of fiery opal. This carving was actually a time portal placed there thousands of years ago by a now extinct race of people. Using their special knowledge, these people had learnt the art of traveling between selected time periods.
Inadvertently activating the time portal, Matt, Josh and Zack are transported to the 1800's. After traveling with Australian Aborigines for some time, they realise they are now in another level of existence. They can only get back by activating the time portal in the cave of the opal eyed snake. Each adventure takes them further away from home. They are captured by Australia's famous outlaws, Ned Kelly and his gang; who are on the run from the police.
The boys eventually manage to link up with some drovers who are heading north. While mustering cattle, they are attacked by a tribe of ferocious Aborigines, experience a stampede and hunt dingoes. After the muster, the boys are kidnapped and taken inland by a drover who is suffering from gold fever. He cruelly forces them to dig for gold, but they manage to escape. They find their way to the sea where they pay the captain of a ship to take them back to Brisbane, not knowing the captain is a notorious slave trader.
They manage to get off the ship at the mouth of the Brisbane River and travel inland. After being attacked by a poisonous brown snake, they find another portal and realise they have found the way home again.