No problem!
Laughing Jack’s appearance should be made if the party lingers a bit too long in one place (about half a day) and will stalk them at night too. He will try and single out travelers in a group he thinks are the weakest. He can and will bite someone which can be a very bad situation if that isn’t treated. If he’s gotten someone in group two infected with his curse via bite, all the better to ambush the party when they least suspect it.
Behaves like a mountain lion following a person on a hiking trail essentially.
I’m wishing you luck in running the system soon! Hope you and your players enjoy :D