I propose we find the father and interrogate him about his son, when he was last seen, any enemies of the father or son, clues on the kidnappers etc.
You and your companions head to the fort and talk to the law-giver.
"They took my son Ulco while he was in the orchards two days ago. We were planning on paying their ransom just to make sure he is returned safely. If you are going to try and rescue him just make sure he doesn't get hurt. These bandits normal harass merchants demanding a toll to pass the bridge. They have killed several people who refused their demands."
"Where is their camp?" you ask.
"Their camp is a short ways to the south east. Follow the main road south and cross the river. From there, follow the river east until you find their camp."
And so you follow the road toward the river.
You cross the bridge and head into the forest following the river.
It doesn't take you long before you hear some talking coming from a valley. There is a camp set up in a clearing between the trees. Your party lays low and observes the camp.
The boy is in a zinc cage. He is guarded by a lasher and a pikeman. A woman tends the campfire with an iron crossbow at her side.