Trailing Kaiwulf - Colonies of Man, #2

A pair of bounty hunters (a big guy who's the brains, and a tiny woman who's the brawn) set out to find a missing person last spotted by an archaeologist on an alien world. The problem?The missing person is in another dimension. Oh yeah -- and he's invisible. They literally didn't see that coming. Jee and Dane get handed a top priority mission. The pay is better than they've earned before as agents for the Trace, Rescue, and Identification League.
After this, they might not need jobs. They're the best there is, and the person, item,  or secret hasn't been invented that these two can't recover. Until now. After all, how do you find an invisible man in another dimension? The archaeologist in charge can't afford this fee, and the military would just take over. So the real question is: who-or what-is behind the request to trail Kaiwulf?