Itâ€™s a family reunion on Supergirl when Jeremiah Danvers returns home after being rescued from Cadmus. The Danvers family tries to put the pieces back together after Jeremiah has been missing and presumed dead for years. Meanwhile, Kara and Alex fight those who believe that Jeremiahâ€™s return isnâ€™t as it seems.
Kara and Mon-El are starting to explore their relationship, but she wants to keep things quiet. Kara doesnâ€™t want everyone to watch and comment on their relationship like they did when she was with James. Unfortunately, Mon-El is just way too excited and announces that they are dating within seconds of walking into the DEO. Leave it to Jâ€™onn to remind them that they are coworkers who are dating, and they need to fill out forms with Human Resources. That will have to wait because there has been a Cadmus sighting.
Cadmus was transporting Jeremiah, but Supergirl and Martian Manhunter were able to rescue him. Everyone is so overjoyed that Jeremiah is back that they donâ€™t question his return. They have never been able to get this lucky before with Cadmus. They are too smart, so why are they slipping up now? Jeremiah tells the DEO that Cadmus has a weapon. They want to destroy National City and blame it on rogue aliens. While everyone is worried about Jeremiahâ€™s intel, Mon-El questions whether or not heâ€™s on their side.
The Danvers have a nice family dinner. Alex is even excited to introduce her dad to her girlfriend, Maggie. Jeremiah seems happy that his girls are doing so well. Eliza is grateful to see her husband, but she realizes that they donâ€™t know each other anymore. Jeremiah has been with Cadmus for 14 years, so itâ€™s going to take some time to learn each other again. Jeremiah is happy to be home and is ready to come back to the DEO. Jâ€™onn agrees that he can come back pending some exams. Mon-El is frustrated since he has been through the ringer trying to be a part of the DEO, but Jeremiah is welcomed back with open arms despite being with the enemy for over a decade.
Mon-El tries to bite his tongue, but heâ€™s too worried about Kara and everyone in National City. Mon-El reminds them that Jeremiah is the only one who has mentioned this fusion bomb; they have found no chatter about a potential weapon in National City. He tries to point out how suspicious it is, but Kara just asks him to leave. Before he leaves, Jeremiah pulls him aside and threatens him with a mysterious truth. Jeremiah says that he knows who Mon-El really is and doubts that Kara would like the truth. I always thought there would be more to Mon-Elâ€™s character and/or backstory, but what could it be?
Mon-El takes his suspicions to Winn, and later, Winn catches Jeremiah breaking into the DEO mainframe. Leave it to Jeremiah to have an explanation. He says that he only wanted to look at old case files to see the work that his girls have been doing. His story checks out, but does it really? Why wouldnâ€™t he just ask his daughters about their work? Or, why wouldnâ€™t he just ask Jâ€™onn to see the case files rather than break into the DEO mainframe? This is starting to feel less like a happy reunion.
The DEO ends up finding the fusion bomb, but thereâ€™s no sign of a target. Itâ€™s clear now that the bomb is a red herring. Jâ€™onn realizes that he canâ€™t read Jeremiahâ€™s mind, and Jeremiah tells him that heâ€™s a changed man. Jeremiah reveals that the arm they thought was useless is actually enhanced. It seems that Jeremiah is working for Cadmus. He claims to be doing it for his daughter, but there has to be another way, right? Jeremiah transfers a bunch of data, and when Alex tries to take her father in, he tells her that she wonâ€™t take him alive. She ends up letting him go, and he takes the data to Cadmus.