Farrell is a leader of The Outsiders in The Kings of Clonmell.
He is a the leader, of a small group who are undermining the small fishing village of Selsey in Araluen. Halt, being the Ranger closest to the village goes to investigate and discovers what is going on. Farrell is deceiving the village using the methods usually employed the Outsiders. Halt sees through the man's facade quickly, having experience with the religious cult in previous years.
Halt later unmasks Farrell for who he really is, a bandit and thief. The villagers initially want to deal out justice to the man themselves but Halt takes him as prisoner, and gets a sworn statement of the Outsider's plan from him. He asks Halt "What are you doing here?", which surprises Halt because he is sure he has never met Farrell before.