Haggarty is a survivor of the great plague. He was welcomed by Project Evergreen into their self sustaining community. One day when a large group went out for supplies, Haggarty killed their leader Walter Fish and stole his family, locking the rest out to survive on their own. He assumed the identity of Walter Fish.
He would again lie and gain the trust to the next group of survivors that came along - Gus and Jepperd. When most of the men were out, he would again reveal his true intentions.