Direct answer
Objectives follow journal display order. Some depend on your choices; follow the active objective in the game.
Result
The merchant Geralt found standing by the side of the road in White Orchard was extremely distraught. He had been hauling some precious goods to the Nilfgaardian camp when his horse spooked and veered off the road, pulling the merchant's cart with it and dumping the whole works in the foggy swamp outside the camp. The poor horse became trapped in the muck and soon was devoured by the monsters who inevitably lurk in such places. The merchant was understandably afraid to go retrieve his goods, and thus asked the witcher to do it for him - in return for a sizable reward.
