Taylor wants Jim to uncover the Sixer spy before the 11th Pilgrimage arrives at the colony, and since Lucas appears close to finishing his equations which would open the portal back to 2149, Taylor places guards at the Terminus. Skye offers Jim an alibi for last week's DNA sample sabotage: she was with Josh playing chess. Also Maddy's computer breaks down and she's desperate to get it fixed.
Skye asks Josh to vouch for her whereabouts, and he agrees. Skye then takes a stolen data tape to the Sixers, but she runs into Lucas instead. Lucas explains that he's finished with his calculations, but the final computations could take weeks, unless he gets access to the colony's Eye. Skye is reluctant, but then Lucas threatens to kill her mother if she doesn't cooperate. Now Skye has little choice.
Jim gets a surveillance camera put on a drainage ditch which the spy might be using to sneak out of the colony. Skye gets Lucas' data inputted into the Eye, and Maddy starts seeking out a replacement for her computer's core. Durwin has one, but he doesn't want anything that Maddy offers to barter for it. Durwin's wheelchair could use a new tire, however.
Skye delivers the data card with the finished calculations to Lucas, and she asks about his hostility towards Taylor. Lucas says that he hadn't trusted his father since August of 2138, and Taylor would be able to tell her why.
Jim sees footage of Skye sneaking through the drainage pipe back into the colony and shows Taylor. To see whether Skye is the true mole, Taylor gives her a piece of intel: there's a supply run to Outpost 3. Meanwhile, Maddy is still trying to get her computer fixed, and asks Reynolds to find her a tire.
The supply run goes through without Sixer interference, and later Mira is livid that Skye didn't tell them about the convoy. Skye claims that she didn't know about it, but Mira threatens to withhold the needed medicine from her Mom if she doesn't continue to cooperate. Skye points out that she talked to Lucas, and Mira seems surprised that he contacted her.
Taylor expresses surprise that the convoy wasn't ambushed, and Jim says that Skye only gave the Sixers the barest bits of needed information. They must be holding something over Skye and forcing her to work for them.
Lucas tells Skye that he's going to return to 2149 and warns her not to return to the colony, because his employers will be coming with the 11th Pilgrimage and will destroy Terra Nova. Meanwhile Maddy gets a tire to give to Durwin for the core, but Durwin says that Boylan already snagged the core for himself. Maddy talks to Boylan to ask him for the core, and she offers to work for him in exchange. Boylan doesn't want the sheriff's daughter close by so he gives Maddy the core for free, telling her to remind Jim of Boylan's kindness.
Skye confesses everything to her mother, who had no idea what her daughter was doing in order to keep her alive. She tells Skye to inform Taylor and that she doesn't need to act as a mole anymore. She's more than ready to die. They embrace and Skye leaves, but soon enough, someone comes for Skye's mother.
Skye tells Taylor about the Sixer cure for syncillic fever and the fact that her mother is still alive. She also tells Taylor that she spoke with Lucas, who has finished his portal calculations. To prove that she's telling the truth, Skye tells Taylor something important that only Taylor and Lucas share: August 2138.
Jim and Taylor try to stop Lucas when he goes to the Terminus. They are unable to stop him and he opens the portal and escapes through it. Meanwhile, Curran (the soldier whom Taylor banished into the wilderness) has delivered Skye's mother safely back to Terra Nova. He also has a sample of the medicine the Sixers were giving to her. Elisabeth is confident that Malcolm will be able to synthesize the drug so that Skye's mother will be able to recover.
Taylor warns the colony that a war is coming with the 11th Pilgrimage. With Josh wondering whether Kara is going to arrive soon, Taylor tells the colonists that they will probably have to fight in order to protect Terra Nova.