Three months after stepping into an alien vessel Tom Mason returns, recalling his encounter with an enemy leader and the long journey back. Meanwhile, Hal and Ben conflict over how to wage war.

While Weaver and the 2nd Mass attempt a dangerous river crossing to escape the Skitters, Tom experiences nightmares of his captivity and is plagued by self-doubt. Ben sets out on a recon mission across the river, and Pope questions the decision to leave Tom alive at all.

After Pope's Beserkers try to force Tom to leave the 2nd Mass, he joins their ranks to keep an eye on them. Ben and Jimmy get more than they bargained for when they attempt to ambush a group of Skitters, and a stranger arrives with the promise of a new hope.

Hal and Ben discover a group of children living under the radar, one of whom is Captain Weaver's lost daughter. Tom's youngest son puts himself in harm's way to contribute to the fight against the Skitters.

A boy who betrayed and deserted the 2nd Mass is found among the rubble of a battle, and leads Tom to an injured Skitter -- who he and Ben say is part of a resistance against the invaders. Hal and Maggie get close on a recon mission.

Hal and Maggie stumble upon a grave of unharnessed kids, including a barely-alive Karen. When an infection puts Captain Weaver out of commission, Tom must get the 2nd Mass up and moving toward Charleston again.

Ben discovers Karen's hidden agenda and the 2nd Mass acquires a highly valuable prisoner, leading to a tense stand-off with the aliens. Inside the hospital, a terrifying new form of invasion is discovered, and Ben reconsiders his future with the 2nd Mass.

The 2nd Mass comes across a girl with a damaged harness on their final push to Charleston, and are targetted by her Skitter-converted brother. Maggie, Hal, and Pope break down in the dark, and Weaver confronts Tector about his past.

Tom and the 2nd Mass receive a warm welcome at their last bastion of hope, led by Tom's former mentor -- but soon realize that he is more interested in shoring up his political power than taking the fight to the enemy.

General Bresler declares marshal law but gets more than he bargained for when the rebel Skitters arrive on the doorstep of the city, asking the humans to help them strike at the Overlords.