When you enter the town , you'll find out about some girl's dad is missing since he went to the Cave Bridge

Blow up this wall

Eventully, you;ll find an empty room. Tia investigates...

Selan will save her, but Selan gets careless too...

You find a room full of monsters. That black ball is the source of the monsters, just whack it with your sword.Then proceed up the stairs and watch...

Go back to the town, go to that girls house again. Her father will be there.Talk to them and you'll recive a dragon egg.