Recovering from the massacre in Oklahoma, the surviving followers of Mathis struggle to grasp what has happened and what to do next. Grace still leads alongside Thompson and other Excalibur agents, while Liz grapples with loss. Elise and Shane continue following Carbon's orders and are faced with their greatest trial yet. With genetic modification under public scrutiny, can the group stay safe from Excalibur's assassins and spread the message about the cure?