A suburban couple is forced to flee from a hostile government after their teenage children begin to show they possess certain powers.

In an effort to reunite with one another, Reed cuts a deal with the Sentinel Services and Caitlin and the kids seek help from someone outside the compound. Meanwhile, Thunderbird begins to teach Blink how to control her powers.

Motivated by a tragic event from his past, Jace throws all the power of the Sentinel Services into finding the Mutant Underground Way Station. Meanwhile, Blink’s vivid dreams lead her to confront Dreamer.

Dr. Campbell attends an anti-mutant summit, attempting to take the Hound program national, and some of the team at Mutant HQ goes on a dangerous mission to stop his efforts.

Polaris learns more about her past and makes a crucial decision that could have impactful consequences. Meanwhile, the Mutant HQ comes under attack and, with everything to lose, relationships are put to the test and alliances shift.

Reeva Payge purges the Inner Circle of those who disagree with her, leaving her completely in charge. Then, fast-forward six months, when the Mutant Underground saves a girl, but not her family, from a Sentinel raid. Against the group's wishes, Eclipse and Caitlin meet with a criminal hacker to get info on the Inner Circle. Meanwhile, Polaris prepares for the birth of her baby, her contractions magnetizing anything metal and wreaking havoc. She also makes Andy promise to save the baby, no matter what.

Thunderbird contacts a mutant lawyer who recruited him to the Underground years ago, hoping she can help him find the Inner Circle. Lauren and Andy have a shared dream, which distracts Andy from his training and prompts Reeva to consider cutting her losses with him, which, in turn, makes Andy second-guess his separation from his sister. Meanwhile, Reed must keep a huge secret from the group and Jace picks up the mutants' trail again

In attempts to stabilize Reed's powers, Reed, Caitlin and Lauren meet with Dr. Risman, a doctor who treats patients with debilitating X genes. However, Lauren finds out Dr. Risman is not who she thought she was. Following the Inner Circle's bank ambush, Thunderbird and Blink continue to work together to chase them down. Meanwhile, Polaris reflects on her troubled relationship with her father and takes steps to protect Dawn from the Inner Circle.

Tensions within the Inner Circle are at an all-time high, as Andy comes to Rebecca's defense against Reeva. After making an important discovery about Dr. Risman's research, Lauren convinces Reed and Caitlin that they must take action to destroy it. Frustrated with not being taken seriously, Jace begins to strategize with the Purifiers. Meanwhile, the Mutant Underground continues to work on saving mutants. However, tensions flare between Blink and Thunderbird as they confront their differences.

The Mutant Underground wrestles with the idea of recruiting the Inner Circle to assist them. Andy considers reconnecting with his family when he learns about his father's powers, but Lauren may not be as willing to have him back as their parents. Find out if the Mutant Underground and Inner Circle will be able to put their differences aside in order to save John from the Purifiers.

Reeva prepares to carry out her plan for the Inner Circle, but not everyone is on the same page. Reed struggles to manage his powers and the family realizes that without enough of the serum, it's only a matter of time before he completely loses control. Frustrated and egged on by Benedict Ryan, Jace and the Purifiers are on the attack, but for Jace, things aren't as black and white as they once were.