Your talking about the framed slayer near the champion harbor right? He's involved with the first quest from Kenneth, if you choose him. If you didn't pick him then you can't really rescue him. You can say lets go and take him to the teleporter but unless Kenneth told you to do so, you get no reward. You'd also fail the quest the guy who wants you to kill him gave you. Unless you picked Kenneth as your trainer just kill him to get the reward from the other guy.
