On the outskirts of Charleston, just steps away from perceived safety, The Mason Clan and the remaining 2nd Mass suddenly find themselves under brutal attack by a new Espheni war machine - and a new, deadly creation unlike anything previously encountered. Divided like chattel and spread to the winds, The Masons must each forge new relationships and abilities to survive.

The Espheni reveal their new plan to Tom, and he is faced with an impossible decision. Meanwhile, Weaver and Pope investigate a way out of the Espheni prison, while Matt struggles to hide his true allegiance from the "Team Leaders" at the Espheni Youth Camp. Elsewhere, Anne leads an exhausting search for her daughter Lexi, while Ben's concerns about Lexi's increasing powers uncovers a devastating secret she's been keeping.

Tom and the 2nd Mass hatch an elaborate plan to escape the confines of the Espheni Ghetto. Meanwhile back in Chinatown, after learning from Ben that Lexi has been keeping a deadly secret, Maggie confronts Lexi publicly. At the Espheni Youth Camp, Matt tries to talk Mira out of a dangerous escape plan. While trekking through the woods with her guerrilla fighters, Anne has a flashback to her time in the Espheni Tower with Karen, where a terrifying secret about Lexi is revealed.

After breaking out of the Espheni Ghetto, Tom and the 2nd Mass seek refuge in a Volm hideout, where tensions run high between the Volm and humans. Tom sets off with Weaver and Cochise to find Matt, leaving Hal in charge. Meanwhile in Chinatown, Anne is reunited with Lexi, and comes to realize that the little girl she saw 6 months ago is now a grown woman.

After freeing Matt from the Espheni Youth Camp, Tom encounters two mysterious strangers in the woods, who attack his family before embarking with him on a violent journey. Hal faces almost insurmountable odds as he tries to lead the remaining Volm and 2nd Mass to a place of perceived safety. Lexi and Anne have a difference of opinions - resulting in dangerous consequences.

After months apart, Tom finally reunites with his family and the 2nd Mass. But the joyous reunion is cut short as Lexi undergoes a health crisis tied to her hybrid DNA. The crisis pits family members against one another as they fight over how to deal with Lexi's illness. Anne goes to great lengths to save her daughter.

Lexi emerges more powerful and ruthless than ever. Tom and the 2nd Mass must work together with the Volm to hold off the invading Espheni forces in what becomes the bloodiest battle of the series.

The 2nd Mass picks up the pieces after a devastating alien attack leaves Maggie fighting for her life... and Hal fighting for Maggie. Meanwhile, Tom and Dingaan are cut off from the rest of the group, buried under tons of rubble, where they must rely on an Enemy Ship to rescue them.

While members of the 2nd Mass attempt to dig out a shot-down Beamer, Tom and a small team follow the Volm to a supply cache in search of equipment to expedite the process. Along the way, they encounter a friend, and must decide whether or not to trust her. Back at camp, Maggie and Ben grow closer as he teaches her to hone her new skills, while Pope and Sara continue to clash, resulting in a fight from which they may never recover.

Tom and the remnants of the 2nd Mass learn to pilot a Beamer as part of their plan to destroy the Espheni Power Core, and the group draws straws to see who will embark on the dangerous mission.

Tom's mission to destroy the Espheni Power Core is complicated by Lexi's return. Lexi is forced to take extreme measures to save her father's life - and her own - after a Beamer malfunction. Meanwhile, the second Mass fears an impending Espheni strike by the scorched Overlord.

With the weight of humanity's survival on Tom and Lexi's shoulders, they must defeat Tom's mortal enemy and find a way to destroy the omnipotent Espheni Power Core. Meanwhile, a new, terrifying Espheni Bomb is dropped onto Chinatown, immobilizing the 2nd Mass and preparing them for Human Skitterizaton.