Season finale. Tensions between the U.S. and the Soviet Union reach an all-time high on the moon, throwing multiple missions in jeopardy.
At mission control, Bill and Aleida supervise Apollo-Soyuz, when a man tells Flight that Jamestown was depressurizing, so he tried to contact them to no avail. Margo finds out, and Rossi comes in, saying that they had been having some issues with their sensors and pressure returns to normal.
At Jamestown, Rossi is held captive by the Soviet cosmonauts who infiltrated. However, all doors are locked. Tsukonov asks for Rolan Baranov, but Rossi does not know where he is, so he gets punched him in the face.
Ed flies through space and thinks about Karen until he is called by Gary, who tells him to sleep, but he does not accept. Gary tells him they are two hours away from the blockade line, which is where they would face Buran. Gary asks him if he is okay, but Ed tells him to get back to work.
Ellen makes it to mission control, where she is told by Margo that the Soviets were asking for more time before docking with no reason given. Margo is optimistic, but Molly tells them it has to do with the lunar blockade. Margo asks about Buran, but Ellen tells her is classified which Margo finds ridiculous since they would not be able to make informed decisions.
Gordo looks out the window of the room he was stuck in with Tracy. They realize the inside was depressurized. Gordo realizes the Soviets had infiltrated the base, so he tells Tracy to hide. Rossi tells the astronauts that he was being held by the Soviets, who were offering an exchange between him and their cosmonaut Rolan Baranov.
Rolan tells the astronauts that they needed to do as they said, but Webster says that it was not up for discussion since they were under the president's order, adding that even if they gave Rolan back, Rossi would probably be killed anyway. Rolan tells them the Soviets would not leave until they had them, but a marine says that they would make the Soviets leave.
Karen walks to Sam Cleveland's building, where he asks if she ever worries about Ed on the moon, so she tells him that she tries not to think about it and tells him that Pot is a good solution. Sam asks her what she would do next, but she admits she was not sure. Sam tells her that if she was having second thoughts it was fine, but Karen tells her she was sure.
Ed tells Houston and his crew that they would pass the blockade point. They do not see Buran on their radar. They ask Houston about Buran and are told that they were on the dark side of the moon, which was a relief for Gary, but Sally tells him not to get confident.
Raegan speaks to the Soviet Union's leader, who tells him that if the United States fired on Buran, the Soviet Union would respond in a substantial way and threaten Raegan.
Sergei tells Margo that they would need to delay docking once more since they needed more time, which Margo does not agree with. Sergei apologizes and tells her that the best he could do would be giving her their state vector for their next docking opportunity, which Margo accepts.
Ellen tells Margo and Molly that they could not keep this up, but Margo does not want to give up since they were on the brink of war. She asks Ellen for one more orbit, and she gives Margo 90 minutes. Molly tells Bill that they had one more orbit before they called it quits, which Aleida protests since people had worked very hard. Molly asks Bill who Aleida is and mentions she likes her when she sees her attitude.
Danielle is angry on Apollo, saying that they did not go that far just to wave at each other from a window. She tells her partner to raise Soyuz. They copy and Soyuz tells them that Orlov continued to struggle with space adaptation, which makes Danielle laugh since he was still vomiting. Danielle tells him that she felt the handshake would not happen and Stefan says the same.
Margo walks to a telephone and types the number that Sergei gave her. He picks up and apologizes and she tells him to come clean with her. He admits that they were having avionics issues, which Margo does not buy, but he tells her that if he told his supervisor that they were having problems, then the mission would be called off. He tells her he was trying to do the best he could, but she tells him that she could only do one more orbit.
Gordo watches the news and tells Tracy there was nothing on Jamestown. He tells her that last time he was there he watched a lot of Bob Newhart, which he nearly memorized and tells her that they would act them out. He tells her that the only thing he looked forward to was fighting with her on the communication device. He tells her that there used to be an antenna which they used which might still work.
The astronauts suit up and grab their guns, walking through Jamestown and depressurizing.
Gordo manages to connect the antenna and Tracy sees that the American marines were moving forward. She calls them and they recognize her, telling them that she was fine. A cosmonaut approaches Vance from behind, so she tries to tell him, but to no avail. Vance is shot and dies, which horrifies Tracy.
The other astronauts realize this and approach the cosmonaut, who shoots another one of the American astronauts. The cosmonaut sees Tracy, but is shot by Webster. Webster approaches her fallen teammate, whose suit was depressurizing. They got him into a pressurized room but the bullet had gone through to a nuclear reactor's primary coolant pump.
Margo tells mission control to contact Rossi, but they get no response.
Margo finds Ellen and Bradford and tells them that Jamestown was not responding. Margo says that there was a backup, but Bradford tells her that it might not be that simple and reveals that there was a second reactor in order to make weapons on the moon which meant there was no failsafe. She tells them to forget that it was nonsensical to have nuclear weapons on the moon, but to keep it from the people in charge was wrong. She storms out of the room after that.
Aleida gets a snack and hears a radio sounding. She walks into a small room and hears Gordo communicating. She reveals herself and Gordo greets her. Aleida walks up to Margo and Molly and tells them about Gordo, so both of them rush with her.
Molly asks Gordo and Tracy if they had been in contact with anyone, but Gordo reveals that the comms had been taken down and they had no suits. Margo tells them that in about 45 minutes there would be a massive nuclear meltdown which would kill everyone on the base and rendering Shackleton uninhabitable for a thousand years. Gordo asks what they can do and is told that they could swap out the cable connectors from the backup computer to the primary loop, but they had no way to reach them with no suits on. Gordo asks how far the cables were and says that he could get to them, but Tracy and Margo tell him it was not possible. Molly defends him, however, and says that if they gave him some sort of protection, he could last longer outside.
Ellen tells Ed about Jamestown and he remembers he put everybody on that base. Sally asks why they would attack Jamestown, but they do not know. Ed tells them that they saw a weakness in them and Bradford tells them that they were their last hope. They start losing signal as they reach the far side of the moon.
At Outpost, Karen pours herself a drink and is joined by Kelly, telling her that she had sold it. She tells her daughter that she sold it because it seemed right and tells her that she did not know what she would do now. Kelly tells her that she could not imagine her doing nothing and is told that maybe Karen would go to India or go back to college. Kelly asks her if she and Ed would be getting a divorce when a siren started sounding. An emergency broadcast started to sound and they both go downstairs.
In NASA's mission control, the siren starts sounding, so Ellen tells them they're in DEFCON 2 since the Soviet fleet off the coast of Panama is threatening the southern United States with ten nuclear bombs threatening Houston alone. Margo tells everyone where the bomb shelters are at, telling them that whoever wanted to go should go, but only one person leaves. Margo tells Bill that they would need to bring Apollo home.
Danielle is not happy about being called home and calls Soyuz, but does not get a response until Stepan tells her he has heard about the news as well. She tells them that she was tired of being used and being told what to do and tells Stepan that at least Laika got to do their mission. She tells Stepan that they should just go for it.
Gordo and Tracy start making an impromptu space suit and are told what to do by Molly. He is asked if he wants to change his mind, but he does not and shuts down their communication. Tracy tells him that she would be going with him since they had a shot at making it back together.
Karen and Kelly watch the news. Kelly tells Karen that she went to see her birth father after looking him up. Karen is in shock and says that she did not know her daughter wanted to meet him, but Karen tells her it is okay and asks her what she was like. However, Kelly tells her that she did not even talk to him since they both had their lives and families.
Pathfinder gets a radio in which they are told they were violating a space treaty and would be fired at if Sea Dragon did not leave immediately. Sea Dragon would be within missile range in five minutes, so Ed tells Gary to open the payload doors, which reveals their weapons.
Bill and Aleida tell Apollo how to get back down, but Danielle refuses and tells him they would proceed with the docking maneuver. Danielle tells him that she would not be going back down. When Margo tells her what her orders were, Danielle told her she was choosing to ignore her orders and told them to begin docking procedures lest they crash. Molly says that she does not care what Danielle had said since she had been given an order, which Makes Margo comment that maybe it was due to it being okay that she had not followed orders many times before. Before Molly could react, Ellen tells them that it was okay for them to proceed since at least one good thing should happen on that shitty day. Aleida does not believe it, but Bill lets her talk to the astronauts, which Margo encourages. Apollo begins approaching Soyuz and they ultimately dock.
American astronauts are being forced to move while Gordo and Tracy covered themselves up. Webster shoots at the Soviets, who fire back at her.
When Tracy and Gordo are covered in duct tape with their suits. Gordo tells Tracy he loves her, and she returns the words. They put their helmet on and run outside with time running. As they move, they start bleeding from the pressure as their suits started coming off. They manage to get it done and start running back. Gordo falls, so Tracy picks him up and they run together. When Tracy falls, Gordo picks her up again and they start losing sight. They passed the fifteen seconds, but made it back into the room and tried to pressurize it once again.
Danielle opens Apollo's door, and so does Stepan. The two of them face each other and greet one anther, shaking hands successfully and smiling at the camera facing them.
Ellen is called by the president, who told her Apollo-Soyuz was beautiful and inspirational, which Ellen felt they needed. Raegan asks for the status of Pathfinder and Buran, who were still out of communication range.
In space, Buran tells them that they had two minutes to leave, but Ed tells them that if they were fired at, they would fire back. Sally wondered if they were bluffing, but Ed did not believe so. He tells her to lock weapons system on their target, but Sally says that there must be another way. Ed says that they have orders, but Sally reminds him that he is commander of Pathfinder and also reminds him of when he testified on Apollo 10. Ed tells her to lock weapons system on target once more, but when she does not do it, he tells her she is relieved of duty. Sally does as he tells him, but points her gun at him. He tells her to put it down, but she tells him it was not a joke. Ed gets up and tells her to shoot him, since he knew she would not shoot him. He points his gun at her as well, and Gary tells them to stop and tries to think of another way.
Buran had missile lock on Sea dragon 17, so Ed sits down again, telling her he would do what he had to and shoots Sea Dragon down. They look at the cosmonauts and turn back from the moon. Houston contacts them and Ellen asks if they had engaged with Buran, but Ed says they had not, which Ellen is relieved to hear.
Raegan flies to Moscow, where he and Premier Adropov decide to stop fighting one another.
At Jamestown, the Soviets start going back.
With everything finished, Rossi and the rest go to Gordo and Tracy's room. They're found slumped over, having succumbed to their wounds and dead due to the pressure.
The United States holds a grand funeral for the two heroes, where they are thanked by Raegan for their sacrifice, courage and service.
Later, at Tracy and Gordo's graves, Ed cries and leaves a deck of cards on top of Gordo's. Molly, Ellen, Danielle, Jimmy, Danny, Karen and Kelly cry as well. Karen leaves Tracy flowers.
After the funeral, Ed and Karen hug and both go their separate ways after Kelly hugs him as well.
Margo gets a call from Sergei, who called to convey his respects. Margo understands and tells her that they were heroes for the entire world. He asks if she would be at the ICSE conference in the UK that summer and invites her for a drink if she goes. She says she would check if she would go, but tells him she would see what she could do.
After the call, Sergei is told he did a good job by a superior, who tells him that by the time Margo realized she was working for them, it would be too late.
Margo, unaware of her counterpart's circumstances, silently reminisces at the grave of John F. Kennedy. The camera pans away into the atmosphere, then overlooking the entire Earth, then panning over to the moon, and finally zooms in on Mars.
The year is now 1995, and a pair of booted feet step onto the red planet, their identity unknown.
- Joel Kinnaman - Edward Baldwin
- Michael Dorman - Gordo Stevens
- Sarah Jones - Tracy Stevens
- Shantel VanSanten - Karen Baldwin
- Jodi Balfour - Ellen Wilson
- Sonya Walger - Molly Cobb
- Krys Marshall - Danielle Poole
- Cynthy Wu - Kelly Baldwin
- Casey W. Johnson - Danny Stevens
- Coral Peña - Aleida Rosales
- Wrenn Schmidt - Margo Madison
- Jeff Hephner - Sam Cleveland
- John Marshall Jones - Nelson Bradford
- Noah Harpster - Bill Strausser
- Leonora Pitts - Irene Hedricks