Sedos Sebile has a quest for you.
All you have to do is find out what's happened to Head Gaoler and she'll reward you for it. This is good as it won't get in the way of your main quest with the Waterdavian Creatures. Once you're done dealing with the prison menace, just head back to her and she'll reward you for your efforts.
Now for the rewards, normally you just get 300 GP, but it doesn't mean you strive for more right. Use either the persuade or threaten action to see if you can weasel more money out of her. But remember that threatening an NPC means that you shift your alignment towards evil. However you can also choose to not take the gold, so that's a shift towards Good.