Denise Cleever works for the Australian Security Intelligence Organization.
This agency has as its primary duty counter-espionage. The work usually entails going undercover, a task in which Cleever has shown a particular talent. Comparable, at least in this series, to America's FBI and England's MI-5, the agents of the ASIO monitor fringe groups, suspected terrorists, and subversive organizations plotting overthrow or mass destruction. They also crack spy rings and monitor security operations to keep Australian secrets where they belong.
Cleever has been an agent for only a short time at the start of this three-book series. She had undergone extensive training and received good reports in all fields. She knows how to handle a gun and how to handle herself in a physical confrontation but she lacks experience in both, making her nervous about both. It doesn't stop her from doing her job but an occasional gulp is not out of the ordinary. Unlike most agents, however, her cases have thus far entailed her going undercover, working alone, which tasks her training considerably, not to mention her nerve. Cleever is still quite young, probably in her mid 20s, and having to be amidst killers and extremists with now ready backup proves understandably tasking.
Of her personal life, little is specified other than she is blonde, though she has dyed her hair for at least one mission, very attractive and alluring, and has a wry sense of humor. She had considerable respect for those who have trained her but not a lot for other authority figures. She has no steady relationship and does not seem too bothered by it. Being lesbian she notices other women but none have made a lasting enough impression to form a bond with.