Mark Holland is an agent with British Intelligence.
For more years than he cared to remember, actually close to two decades, Holland worked for the "Department", an unnamed arm of the British Intelligence community. While there, he performed the normal duties of a well-trained operative. Some people he tried to bring into the country while some he tried to keep out. All the time working there, he had to deal with a superior named Willis who disgusted him.
Finally he had had enough of that life. He left. He was given a very good separation package and help in the papers to start a new life in Geneva but he was told that "no one ever really quits the Department." He intended to be the first.
Needing a new career, he took up his greatest passion, music. While neither a musician nor a composer, he knew enough about both, not to mention a good understanding of the business end so he was able to start a business representing musical artists. His new life was to help them arrange their concerts, contracts, and often their lives. He proved to be very, very good at it and he loved it.
Both financially and personally it was quite profitable and, as the series begins, he has been doing it for seven years. Seven years without every hearing the odious voice of Willis telling him about another assignment where he would have to put his own life at risk or possibly see to the end of someone else's. Then his former life came calling again and Willis reminds him of the truth of his profession and Holland is again dodging bullets and bombs, this time while juggling show dates.