Wollombi, The Hunter Valley, 1847: The last thing Mellie Vale remembers before the fever takes her is running through the bush as a monster chases her - but no one believes her story. In a bid to curb Mellie's overactive imagination, her benefactors send her to visit a family friend, Anthea Winstanley. Anthea is an amateur palaeontologist with a dream. She is convinced she will one day find proof the great sea dragons - the ichthyosaur and the plesiosaur - swam in the vast inland sea that millions of years ago covered her property at Bow Wow Gorge, and soon Mellie shares that dream for she loves fossil hunting too... 1919: When Penelope Jane Martindale arrives home from the battlefields of World War 1 with the intention of making her peace with her father and commemorating the death of her two younger brothers in the trenches, her reception is not as she had hoped. Looking for distraction, she finds a connection between a fossil at London's Natural History museum and her brothers which leads her to Bow Wow Gorge. But the gorge has a sinister reputation - 70 years ago people disappeared. So when PJ uncovers some unexpected remains, it seems as if the past is reaching into the present and she becomes determined to discover what really happened all that time ago...