Rick Bernard is an agent with the AIU.
So is Summer Sawyer who is nearly as important to the series as Bernard but is not given series title credit by the publisher or author. That remains the domain of Bernard alone.
But first the AIU. That appears to be an organization with an unusual concept.
The acronym comes from the designation given each of the operatives chosen to work for the group. As was explained to Bernard a dozen years before the first recorded adventure takes place, "The CIA, DIA, NSA, FBI all have intelligence missions. They are required by law to only work in certain theaters of operation. They only seem to communicate fully when there is a crisis and usually after the fact, like in the aftermath of 9/11. Your designation would be agent/intelligence/agency unassigned. By being unassigned you can avoid the red tape and legalities of being assigned to one agency."
The interviewer back then continued the explanation with "your assignment, as we see it today, would be to act as a deep cover agent. We would set you up in a great job and the vast majority of the time you would be doing that work. Occasionally, we would call upon you to do something for us, mainly surveillance or courier work. Nothing that would be dangerous or violent would be in your job description. You would have that job until we needed you elsewhere or you retired. Our service would help you to be successful and happy. We would send you to training for the work I have described in such a way that your family and friends would never know what you were doing. We will expect you to keep this position confidential and you will not be able to tell anyone including your immediate family. There will be benefits that you cannot at this time imagine."
This interview took place during his third year at Loyola University in Chicago and for the rest of that year and all of his senior year he waited for his first assignment and when it finally came just before graduation, it was a let-down. No fast cars and exotic settings and certainly no gorgeous femme fatales awaited him. He was told he would be a Chicago Public School teacher.
If you think this is all rather strange, you are not alone as Bernard did as well. He would find that strange would become a new norm for his work with the AIU.
As for Summer Sawyer, she will become an AIU operative and will work alongside Bernard, putting her life every bit as much on the line as Bernard. The interesting aspect to their relationship is that she was his assignment in his surveillance lessons.