The National Guard take steps to close down all tunnels in and out of the cordon on Day 19. Lex gets a letter from Interal Affairs during an argument with the National Guardsman in charge. Meese alerts Jana and the others that their quarantine is up and it's time to move, but first he wants the second half of his payment. Jana sense something strange in his demeanor and refuses to pay until they all make it out safe.
Inside the cordon, Jake finds Dr. Cannerts inside Cinco's quarantine room with Thomas. In order for the treatments to work, Cannerts needs to draw blood from Thomas in real time. The treatment is straining for Thomas and Jake demands Cannerts' stop but he refuses. Micheline's infection grows more severe and Bert decides to go out in search of medicine.
After Thomas is safely back in his room, Cinco begins seizing and dies.
Meese leads Jana and her friends through the tunnels. Suzy fights against her claustrophobia when they hear dynamite blowing up part of the tunnel system. They discuss the risks versus rewards of moving forward or turning back and decide escape is the only answer.
Lex meets with the Internal Affairs investigator who is looking for information about how someone managed to escape the cordon. They suspect Lex is responsible for the escape, but instead of handing over Meese and the Captain, Lex decides to walk out of the interview.
Jake leaves the furnace room and finds Trey attacking Dr. Cannerts. He manages to calm Trey down and when he leaves, Jake tells Cannerts that Cinco didn't look like the other bodies he's burned. Cinco didn't die from the virus.
At Lex's house, police issue a search warrant looking for any information connecting Lex to the cordon escape. His father makes a scene to divert from the fact that he pocketed the one thing which would benefit the OPS investigation. Lex and his father can't find Leo Green and they need his help to take Lommers down.
There are more explosions in the tunnels and Teresa, Xander, and the baby are separated from the rest of the group. Jana tells them that they'll circle back, but Teresa sends them forward. She and Xander turn back to the cordon.
Cannerts does more tests on Cinco's body to determine what needs to happen in order for his treatments to work. The problem is that Thomas, so far, is their only source of antibodies. Jake decides they should test everyone in the cordon to find more people who are immune but no one wants to help.
Outside the cordon, Lex finds one of his officers who isn't supposed to be working and grows suspicious about the switch. He finds the officer responsible for helping people escape from the cordon and learns that Meese is in on it too. Walden thinks Meese fell inside the cordon on accident and is shocked to learn the fell on purpose. He's even more shocked to learn that the tunnels are being blown up.
Cannerts finds Jake in the furnace room where he's staring at the jars of ashes and lamenting the fact that no one will help them. As the men talk about Katie, Jake gets an idea. Meanwhile, in the tunnels, walls continue collapsing. Meese has no idea how to get them out.
Jake stands in the middle of a park and calls out the names of those who died and uses them as a plea to get people to have their blood tested. Lommers watches as pundits argue over Syria when Lex enters the briefing room and tells her that Meese is helping people try to escape and that there are people in the tunnels at that very moment. She gives him one hour.
Bert returns without medicine and Micheline asks him to open the good bottle of wine.
Cannerts and his remaining medical team set up tables outside the hospital in hopes that people will show up to be tested. Trey shows up with two of his men and offers to have his blood tested. Others begin arriving in droves.
Lex takes some of his men into the tunnels and on the way gets a call from his dad. He's located Leo. Lex asks his father to carry on with their plan to take down Lommers no matter what happens.
Xander, Teresa, and their baby make it back to the market. She decides they're done running and makes him stay. They plan to clean it up and restart their lives there. Jake and Cannerts find another person carrying the antibody.
Lex instructs his men to walk through the open tunnels searching for anyone who may be inside. Meese gets Jana, Suzy, and Quentin to the rendezvous point but his contact is nowhere to be found. Roy meets Leo in a hotel room and delivers the information Leo needs to take down Lommers.
While walking through the tunnels, Lex finds Quentin's hat and tells Lommers there are kids inside the tunnel. She gives him 20 minutes to get people out. Meese encounters Walden and shoots his partner so that he can get Jana, Suzy, Quentin, and himself out.
Bert crushes up cyanide and pours it into a glass of wine for Micheline, at her own request. Later he reveals he doctored his own glass too.
Lex stumbles upon the people trying to leave the cordon and realizes it's Jana. He doesn't know what to do. Lommers tells him time is up, but she's informed there's no signal from his walkie. She gives the order to resume imploding the tunnels just as news breaks about Lommers' guilt.
Jake heads onto the roof of the hospital with Katie's ashes as Jana, Suzy, Quentin, and Lex re-enter the cordon.