The "Revolution" episode "The Children's Crusade" opens with a group of Monroe Republic militia holding Charlie down against her will. Another militia member sticks a branding iron in the fire, heats it up until it is red hot, and brands Charlie with the "M" that marks all militia members.
The episode flashes back in time to two days previous, where Charlie and the group walk through the woods and see a teenage boy being taken away by the militia. Charlie wants to help the boy, but Miles tells her to stay down. Later, the group encounters an unconscious boy. When they stop to help, though, the boy jumps up and runs away. It's an ambush: Charlie and the survivors are quickly surrounded by a mini-army of teens and children.
The kids interrogate Charlie, thinking that they were responsible for stealing Peter, their leader. Charlie asks what Peter looks like, and then explains that she think she saw the militia taking him away in the woods. It is revealed that Peter and the rest of these "lost boys" were orphaned after their rebel parents were killed by the militia.
Peter's brother Michael starts to rally his troops for an attack on the militia, but Charlie doesn't want the kids to be killed by taking on a superior force. Charlie offers to go in Michael's stead and rescue Peter, because she understands what it is like to lose a brother to the militia. However, Michel and three of his young friends follow Charlie and Miles on their quest.
Meanwhile, Danny is growing increasingly angry of being confined, but Rachel tells him to stay calm. Monroe has abducted one of Rachel's colleagues from before the blackout: a doctor named Brad. However, Brad isn't talking about the pendants, despite being tortured.
In a flashback to three years before the lights went out, viewers learn a bit more about the mysterious power pendants. Ben and a pregnant (but ill) Rachel stand alongside Grace and Brad as a man from the Department of Defense gets a sample of the power going out.
The pendants were created in an attempt to generate clean, low-cost electricity, but Ben and his team failed, instead creating an ability to turn off the lights. The D.O.D. guy is prepared to offer them a contract. Ben wants to take it, since the company is nearly out of money, but Rachel worries about the tech being used as a weapon.
The only way to rescue Peter is to get taken along with the rest of the conscripted teens, who have been taken prisoner on a conscription vessel. Whiles Miles worries about his niece, Charlie tries to steal a set of keys and free Peter, but she's caught and branded instead. Miles, Nora, and Michael go to the ship to free Charlie and Peter.
Back on dry land, Aaron's pendant spontaneously activates, turning on a whole lighthouse. The bright light it creates catches the militia off-guard, giving Miles and his group a chance to get the drop on the enemy. When Miles comes back to shore, Aaron tells Miles and Charlie that Ben gave him the pendant and explains what it does.
In one final flashback, Rachel is wooed by the D.O.D. representative. He can offer her entry into a clinical trial that might save the life of the child in her womb... if she will cooperate with him.
Elsewhere, Grace is revealed to still be alive and is being held prisoner by the same man from the D.O.D.: Randall Flynn.