Mon-El wakes up alone in bed. Kara flies in through the window with coffee and flowers.
Kara and Mon-El go to stop a Cadmus attack and find Jeremiah alone and chained up in a truck. They bring him back to the DEO and Alex can't believe it.
Mon-El points out that they got an alert about Cadmus. He's suspicious. Jeremiah tells them Cadmus has built a new radiation bomb based on Kara's heat vision.
The family has dinner to welcome Jeremiah home. Alex introduces him to Maggie. Mon-El's suspicions cause tension. Jeremiah reveals that he knows who Mon-El is.
Mon-El asks Winn for help and he agrees. Winn finds Jeremiah breaking into the DEO mainframe and tells Kara that he's spying on them. Jeremiah claims he was just looking at case files.
Kara starts to grow suspicious, which causes an argument with Alex.
Winn tracks down the bomb. Alex and Kara arrive, but there's nothing there. J'onn discovers Jeremiah is not who he says he is and they fight.
Alex and Kara return and J'onn tells them what happened and that Jeremiah's arm is enhanced. Winn announces that he hid a tracker on Jeremiah.
Kara and Alex track him to Lillian, but Kara has to go save a train of people. Alex chases after Jeremiah.Alex can't bring herself to shoot him, and lets him get away.
Winn finds out that Jeremiah stole the national alien registry.