Set in the exciting world of the underground tunneling industry in Sydney the story follows the career of Peter Brown a tunneling engineer and his relationships with his colleagues and family, and in particular, the development of the relationship with his daughter from childhood to young adult. The story line explores the potential for terrorists to use this urban underground domain to cause havoc and destruction in the city, with sleepers entrenched in the Australian society who are then called upon by their leaders to serve the cause. The cast is also filled with a number of interesting characters who are evident within the Australian construction industry, all with their own little personality traits. Through this we follow Peter's career development from engineering to anti-terrorism, as he develops more and more exciting and complex underground construction works in Sydney.