Scott needs to search for the skitters' communication frequency signal with his transmitter, but before he continues, Tom tells Anne that he's nervous to torture Ben by making him listen to the painful signal. Anne doesn't really have many answers since this is a totally new medical phenomenon for her. She tries to comfort Tom, who's nervous about Hal, gone away with the fighters, and Ben. While the rest of the group leaves to do errands, Scott stays behind to work on his transmitter. Something catches his eye in the corner of the lab -- it's Rick. The boy is miraculously wedged at the ceiling and screams that he won't let the old man hurt the skitters. Right before he lunges for an attack.
Meanwhile, the caravan of fighters heads toward the city. Weaver shows signs of instability, but only Hal seems to notice.
Ben guesses that it was Rick who attacked Scott and also broke the transmitter. He finds Rick hiding on campus and tells the confused teen to return the part he stole from the lab. Rick seems to have an allegiance to the aliens, and he says he wants the harness back, to return to the skitters. Ben screams for help, but Rick has already jumped through the open window to escape. Ben runs after the teen, creating panic in the rest of the 2nd Mass that the two will divulge their location to the aliens. Rick manages to outrun Ben, so it's up to Tom to retrieve the teen.
While walking through the forest, Rick finds one of the harnessed children. He asks to come back but before that can happen, she orders him to tell her everything that he knows about the 2nd Mass.
Close on his trail is Tom, who finds a desperate Rick alone in the forest. He says that the skitters have forsaken him; he doesn't fit in with anyone anymore. Finally, we see the real Rick, who begins to mourn for his father and admit that the skitters only wanted information, they never really loved him. Tom tries to comfort the boy but is shocked to learn that Rick has told them everything about base camp, the Mason family, etc.
The fighters approach the large alien structure back in the city. They assume that the 4th and 5th aren't coming -- their remaining choices are retreat or carry on. Pope speaks up and says they're called the resistance for a reason, and that backing down is no longer an option. The plan is to break up into four squads and blow up each leg of the structure, and get the hell out.
Meanwhile, Tom escorts Rick back to the school. He tells the group that the skitters know where they are and they'll need to evacuate the civilians. He will stay behind with a small group of volunteer fighters to take out the skitters that come to the area. The plan is risky, but it's the only one they have.
Hal comes back from his scouting mission and tells Weaver that the mechs appear to be prepared for an attack, and that the other squads may have been eliminated. Weaver orders Hal to return to the school and tell his father to evacuate the civilians. The captain and the rest of the men will stay where they are and try to destroy as many aliens as possible. He wants Hal to give the rest of the 2nd Mass hope. The young fighter leaves the rest of the men, who are now on Plan C.
At base camp, the civilians prepare for evacuation. Matt apologizes to his father for talking to Pope but Tom says disobedience is just a normal part of growing up. The children are the first to leave, and Anne bids goodbye to Lourdes.
Scott tries to reassemble the transmitter with Ben's help, but Tom doesn't want his son around when the mechs attack. Unfortunately, Ben must stay around since the frequencies keep changing and he's the only one who can hear them. His father begrudgingly concedes.
The fighters assemble outside the school and prepare for the mechs' approach. The humans finally open fire with Pope's mech ammunition, and take out the robot. But the attack isn't over yet. An army of mechs approach base camp, and it looks like the team is out of ammo and luck. Scott and Ben scramble to find the right frequency and stave off the attack -- they can use the flagpole as a stronger antenna. Ben goes outside to connect the signal to the flagpole, but Tom runs to help his son. The frequency gets blasted out, bringing Ben to his knees and driving the mechs away. The aliens retreat and the 2nd Mass gets some much needed good news.
Hal returns to base camp and tells his father that Weaver and the remaining men are going to try and complete the mission. He reports that the roads are clear, which means that Scott's jamming signal may have worked. Tom runs to the medical ward, to tell Anne that he won't be going with the civilians right away. He wants to help the men stuck in Boston. But he asks the doctor to watch out for his sons if something happens to him. He kisses Anne goodbye.
Scott hooks up the transmitter to the GTO, so the car functions as one big antenna. Tom will drive it into the city, alone, without the help of his sons. He arrives in Boston and finds Pope and Anthony injured but alive. Tom is going to continue on and look for Weaver, while the two men take the GTO back to camp.
Tom finds a confused Weaver within the rubble. He believes the alien ships are being called back to wherever they're from, perhaps because of Scott's jamming signal. Before they retreat, Tom wants to use the bazooka he brought. It turns out that his aim is pretty good and causes more damage than expected.
Weaver and Tom head back to camp, but see a harnessed Karen in the middle of the road. She tells Tom that the aliens never expected resistance here on Earth and want to "talk" to him. He's angry that these beings want to negotiate after murdering millions of people and stealing human children, and Weaver wants to kill the alien standing next to Karen. She says they shouldn't because of Ben -- the harness is a process and the young boy will be called back unless his father goes with her and the aliens.
Karen says the aliens can force Tom to go with them, or he can go willingly. The caring father puts the safety of his child ahead of his own and boards the alien ship, leaving Weaver to look on in disbelief.