Polaris' baby begins to suffer from a deadly illness, leaving the Inner Circle unable to heal her, and prompting them to turn to an unexpected source for help. Meanwhile, Reed and Lauren take an excursion to deliver illegal meds, but Reed's powers complicate their plans. Then, Thunderbird and Blink meet the leader of the Morlocks - a shadowy group of mutants that live underground - who offers to help them find the Inner Circle, but the two factions may not have the same goals.

When one of the Inner Circle goes missing, Reeva intensifies security in their compound, but realizes that her plans may have already been exposed. Furious and paranoid, Reeva resorts to violence. Caitlin and Reed consider using the serum to restrict Lauren's use of her powers, hoping it will help her as she wrestles with nightmares about the Inner Circle and her ancestors. And it's the battle of two extreme ideologies when the Morlocks and the Purifiers come face-to-face in battle.