Isaac is EnCLaVe and Rosalind's first born son. He is a college student in the events of VGC3 and a full grown man in the events of DFoS. He is incredibly intelligent and a major ally in combatting EnCLaVe's crazy plot to destroy reality. Without him, Abe and Jeremy would never have been able to defeat EnCLaVe. He helped them build a device that allowed them to travel to EnCLaVe's source of incredible power, The Realm of Induction. He joins the party briefly in DFoS and mainly wields Frontier Justices for weapons.
Near the end of the game, Walter ends up doing serious damage to Isaac, resulting in his death shortly afterwards.