What if you make it the Hurricane King himself? He’s been the Hurricane King for so long that his paranoia could easily be causing him to sabotage those he sees as potential threats, using loyal free captains to guide events, and if he sees his loss of power on the horizon, why not ally with Cheliax in order to maintain his position?
You can easily replace Harrigan with another free captain (one of the ones detailed in Isles of the Shackles perhaps), or even several different free captains who are all known for their support of the Hurricane King, and drop clues directing the party to Bonefist.