Australia's arid interior is often called the dead heart. In fact, it teems with life, supported by a hidden network of buried rivers recharged by rare but heavy rains. This episode tells the story of this surprising desert - formed when the climatic change overtook and dried out central Australia. What was once a land of vast lakes and broad rivers turned into a parched region of glittering stone and burning sand, interwoven with swathes of hardy woodland and plains of desert grass. A great variety of plants and animals has adapted to life in the arid centre, with its swings between the brief good condition that follow the unpredictable rains, and then long periods of drought. It's the land of the lizards - from giant goannas that sniff out snakes hiding under the sand, to the tiny, delicate Lake Eyre dragons who've made the desolate saltpans their domain.