Grace Chu and John Knox are agents with Rutherford Risk.
More accurately, they are independent contractors working occasionally for Rutherford Risk, making them, when they are on the job, literally Risk agents.
Rutherford Risk is a very large, quite successful, international investigative organization - 'round the world private eyes. It handles a plethora of different assignments as might be needed by its many clients. Most of those using its services are even large corporations doing business in all parts of the globe and often running into situations which need skill sets outside their normal employees, even the ones that have huge security departments of their own. At other times, the clients are government agencies like the CIA or MI-6 wanting something done and not wanting their own fingerprints on anything.
Rutherford Risk charges a lot of money for their services and they pay their operatives, full-time or contract, equally well which is why people like Chu and Knox are available when the call comes in - the money is just too good to pass up. So is the excitement.
When not on an assignment for Rutherford, they have different, independent jobs and lives. Problems that need solving will throw them together and they will learn that together, they are very, very good even if sometimes being together is less than desired.
Grace Chu is a highly trained and skilled Chinese forensic accountant working out of Hong Kong and called in by a good number of companies to ferret out details, usually in their own firm, that someone is wanting undisturbed. Fraud, embezzlement, unauthorized graft, stock manipulation, and other naughty activities are her special targets and she is very good at finding them. Rutherford uses her a lot when their clients need someone of her skill set.
John Knox is an American import/export businessman in Shanghai whose experience in combat over the years has made him able to keep alive in regions where someone of his ethnicity or national origin might be a tempting target. He truly enjoys the finding, haggling, and exchanging of a huge variety of objects for a good profit but it seldom provides the endorphin-laced rush that the assignments brought to him by Rutherford can and he is honest enough to admit that to himself. Plus the money is very good.
Chu and Knox are not partners. They each have their separate lives and careers. On a few occasions, though, they are thrown together for a job and they find to their surprise that they can, after some early glitches, work well together.