It was so obviously a setup, I a m confused why he accepted the quest.
"oh, you got a mission to carry something valuable entirely alone to a destination~ And if you fail, lose/damage part of the parcel, or are too late, we will take ownership of your slave we randomly decided is collateral~ We won't tell you any details on the request, including how likely you are to be attacked and by who/what, and turns out the actual parcel is just some gold-coins. Precisely a good sum for if you were to pay compensation for a magician and some thugs to assault an adventurer of your rank, walking alone~"
Only question is if guild master was truly part of the "request", or if it was all that clerk. The fact he wasn't killed suggests she might have been.