Explore the area around the camp - main quest BG: Siege of Dragonspear Guide
After setting off with the expedition, you will watch a cut-scene. When it's over, you will automatically find yourself in the Flaming Fist camp in Coast Way Crossing (M7,1). Start from talking to Schael Corwin. It is good to convince her to join your team. The main hero will decide to search the area around the camp. You can leave the camp immediately (head north-east) or look around the camp first (you can for example join a few characters to your team here).
Follow the main path until you reach a blockade on a bridge located in the north-eastern corner of the map (M7,5). You should prepare well before going there, because you will be fighting Caelar Argent mercenaries right after watching a cut-scene. You cannot win the battle, but only last until another cut-scene. However, it is not easy because the mercenaries' attacks are strong and can quickly kill your team members. A good idea is to order the members to attack Seed, Kerry Tinbasher and Elwood Dowser, as these are the enemies that use magic. In the meantime, avoid the attacks of other enemies, especially Barachusa, who deals a lot of melee damage.
As it has already been said, you have to fight until you see another cut-scene. On the opposite side of the destroyed bridge, Caelar Argent will appear and a conversation with her will start automatically. The choice of dialogue options is not very important, because you won't provoke another fight or make her surrender.
When the conversation is over, head back to the camp (M7,1). Talk to captain Corwin and Bence Duncan. Next, go to the edge of the map. To continue the main story, you have to head to Boareskyr Bridge. The only path leading there is through Troll Claw Woods.