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.
- Ben has a steamy dream about getting it on with Maggie, in which Hal comes in with a bloody wound asking where he was.
Ben is awoken by Maggie pounding on his door. She tells him about the Espheni escaping and that they think Lexi helped.
Lexi summons Lourdes to her room, and asks why humans fear change. She tells Lourdes her father is coming. When Lexi asks to be alone, she reveals her hand is turning slimy.
Outside the walls to Chinatown, Hal thinks he sees something in the moon. He's interrupted by two men with guns. But then Tom and Weaver arrive and tell the guards to disarm. The Mason family has a reunion as Hal greets his dad and Matt and then Ben and Anne join them. Then Anne pulls Tom aside to try and explain what's happened to their daughter.
Meanwhile inside, Lourdes brings Lexi some tea and is freaked out by what she finds: Lexi sleeping in a giant glowing chrysalis.
Meanwhile, the members of the 2nd Mass check out Chinatown, including the stationary Mech that Lexi stopped. They're greeted with food and clothes.
Tom and Anne try to have a quiet moment, but Lourdes interrupts. She takes them to see Lexi. Anne freaks out and wants to cut Lexi out of the chrysalis, but Tom cautions her that they have to figure out what they're dealing with first -- they don't want to hurt her. Anne tells him about Lexi thinking an Espheni is her father and conspiring with them.
Out in the courtyard, Hal finds Maggie. Before he can get into his speech about wanting her back, she kisses him. Ben interrupts to bring them to Lexi.
The Masons meet in front of chrysalexi, where Kadar compares her to a butterfly. Anne mentions she's been having memories of Karen and being inside a cocoon. Kadar suggests trying to jump Anne's memory to see how she escaped the cocoon unharmed.
In his makeshift doctor's office in an abandoned eyeglasses store, he injects her with something and talks her back into her memories of her children. Anne remembers being with her son Sammy seconds before the attack and watching him die in front of her.
When she wakes up, Tom thinks she should stop, but Anne is resolved to do what she can to save her other child. She doubles the dosage and injects herself over Tom's objections.
Tom goes to check on ChrysaLexi. Weaver comes to check on him. When Weaver touches the cocoon, it burns his hand. Hal comes in to talk plans for stopping the skitterization camps. Tom says he needs to take a day to be with his family.
Later that night, Maggie briefs the 2nd Mass on Lexi, saying she is a threat to everyone, and they have to do something if they want to survive. Hal joins them. Maggie explains Lexi's powers and that she's been meeting with an Espheni. Pope shouts out that they should kill her. Tom joins them.
He argues he's capable of making tough choices, but nothing will happen until they get more information. Tom takes a gun to make his point.
Hal follows his dad, who lays into him for plotting against his sister. Hal reminds him of the Espheni warping Karen into a threat and Tom recognizing that and shooting her when Hal couldn't. But Tom is determined to protect his daughter.
Ben finds Maggie, asking her to remember how happy she was when he first came to Chinatown and how she told him the Mech stopping was a miracle. He pleads with her to remember that and have hope, but she refuses.
Anne remembers being on the Espheni ship and Karen telling Anne that Lexi is her creation and in time she'll become just like Karen, but better, and together they will end the war. Karen told Anne that Lexi needs her for now, but soon she'll be all Karen's. Karen put her in the cocoon with the baby and sealed them in.
Anne wakes up and starts hyperventilating that she can't save Lexi.
Then she sees Kadar trying to wake her and realizes she's still unconscious.
Tom finds Lourdes and asks her about Lexi. She tells him that Lexi is uniting them. Tom asks for her help protecting Lexi, but Lourdes doesn't think she needs it.
Hal vents to Dingaan. Shaq the Volm joins them, saying that when Espheni hatchlings emerge they're at their most violent and in the worst case, she might kill them all. He tells Hal about his men encountering cocoons and getting burned to death when they tried to cut into one.
By Lexi, Tom finally sees how badly Weaver's hand is burnt. But then al, Pope and Tector come leading a horde of people ready to kill Lexi. Inside, Lexi's cocoon glows bright red and makes a loud thrumming noise. Tom, Ben, Matt and Weaver stand guard by Lexi.
Weaver tells Tom that from a military standpoint, she's a threat, but as a father, he would die before he let anyone hurt her.
Tom confronts the gathered horde. Hal and Pope argue something needs to be. They ask Maggie to repeat what she said, but instead Maggie says she's not ready to say Lexi needs to be killed. Maggie joins Ben standing against Hal.
Hal tells Tom the Volm are leaving. He reminds Tom what he told him when he came off the Espheni ship, that Hal had to stop him if he ever did anything to put everyone at risk. But Tom says he'd never risk everyone and Lexi is still his daughter.
The horde disperses as Tom promises to deal with Lexi by any means necessary if it comes to that.
Back with Kadar, Anne is still having an out of body experience. Kadar injects her with something to try to revive her, but she's still out. Then she sees Lexi sitting next to her. Lexi tells her mom she's sorry about Sammy and she knows Anne wants to save her. Lexi takes her mom's hand and brings her back to her memory on the Espheni ship.
Lexi tells Anne that she'll always need her and she doesn't need to be saved. Lexi helps Anne wake up.
Anne runs to Lexi and tells the group that she won't hurt them. Anne puts her hands on the cocoon, which doesn't hurt her, and assures Lexi that she's there for her.