Tom uncovers confidential intelligence about the heart of the alien operation. Meanwhile, Charleston prepares to mount an offensive against the Espheni, but a massive explosion brings the operation to a halt. And the identity of the mole is finally uncovered, but not before more blood has been shed.

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.

Injured, Tom takes refuge with a unique family who has distanced themselves from the fight, giving him a glimpse of life without war. Hal and Isabella's romance grows as they search for a missing Tom. Meanwhile, The 2nd Mass locates an Espheni device that could be a linchpin to winning the war if they can figure out how to use it. And Maggie makes a decision that has consequences for her and the entire 2nd Mass.