My Dear Gaspar,
We cannot rest on our laurels. True, we managed to convince the witcher to drink the concoction we had brewed without much difficulty, but now we must gather information. Somehow I doubt this Gerard, or whatever his name was, truly will truly keep an experiment diary, even if by some miracle he is literate. And without hard data, the Academy's governors will never renew our grant - believe me, I've been down that road before!
To keep one step ahead of events, I've already taken appropriate action. To be precise, while in Flotsam I hired a spy who will follow our witcher's every move and observe his deeds, especially those performed in the alcove. If our calculations are correct, within a year's time his sterility will be reversed - proof of which fact should come quickly in the form of expanding female bellies, if the rumors about him contain even a grain of truth.
The spy's wage is costly, true, but I'm convinced this investment will yield dividends. I believe a potion which restores the ability to reproduce to those who have lost it due to magic or alchemic experiments will be in high demand - and earn us a fortune.
P.S. Just remember - not a peep about this around the department, or the ethics committee will flay us alive.
P.P.S. I've received the spy's first report. The witcher is headed to Loc Muinne. Perhaps it's a good time to visit?