When entomologist Emlyn Rees arrives at Hidden Valley she wants nothing more than to escape her marriage breakdown by burying herself in the research team's hunt for new species of insects in the depths of the dramatic Undara lava tubes. Travis Carlyle is initially resistant to letting some city folks tramp over his cattle station, though the researchers' findings bring opportunities to turn around his struggling farm. But when things start going wrong for the farm and around the dig site, Emlyn and Travis are at a loss to understand why. As the unseen saboteur grows bolder, Emlyn and Travis are caught in a race against time to save the station...and their lives.