Simon travels from Darwin in Australia's Northern Territory, or Top End, across to the remote Cape York Peninsula, and on to the Great Barrier Reef.
Simon sets off from Kakadu, the largest national park in the world, where the wildlife is under threat from the march of millions of poisonous cane toads. He joins a team of toad-busters catching the amphibian invaders - originally introduced to the country to kill pests.
In Robertson barracks, Simon meets Australia's best - and only - tank regiment. They will soon host 6,000 American Marines - evidence of Australia's strategic importance in the Asia Pacific region.
Simon also heads out on patrol with Norforce, a unique military unit who use ancient aboriginal knowledge to help them survive in the bush. It's a case of green ant tea before bed.
On the Cape York peninsula, Simon joins scientists catching deadly box jellyfish, whose venom could prove to have great medicinal value. And on the Great Barrier Reef he dives in search of the starfish destroying coral, before flying 100 miles out into the ocean to watch as a huge tanker is expertly guided through the fragile reef.