Supergirl's battle with Reactron explodes out onto the streets of Metropolis,and Neutron doesn't care what happens to innocents! And as civilians fall, Supergirl makes a vow so impossible and startling, even Superman doubts she can keep her word!
Superman finds Supergirl in a giant crater in Death Valley after her fight with Reactron. He tells her that next time she should just "beat up the bad guy." She agrees but can't help wonder how Reactron's powers are even possible. She doesn't understand how he can even have a normal mind. Superman tells her that it's their job to bring in the bad guys. People like S.T.A.R. Labs handle the studying part. She wonders if they'd even know how to handle him or what questions to ask. Superman interrupts her as he sees that a couple buildings in Metropolis are in trouble. Reactron is causing problems. Superman tells her to get the people out safely and he'll deal with Reactron.
When Kara tries helping the people, some are put off that they didn't rate high enough to be saved by Superman. She then finds a frightened little boy hiding under a desk. When he sees her, he said he knew she'd come for him. He tells her his name is Thomas and she tells him he's not going to die.
A stray blast from Reactron hits the buildings and they won't be standing for long. She has a hundred and twenty-seven people to save. Moving fast and not being able to be gentle, she takes some out but causes some injuries. Superman then comes and tells her he'll get the people and she can take on Reactron. As he streaks off, she says she's sorry.
Reactron is surprised that Superman "ran away" from him. Supergirl arrives and punches him in the face. He actually feels it but starts laughing as she keeps punching him. When she asks why he's laughing he says it's because his consciousness is floating in space a million light-years from there. She wants to know what he is and what he wants. Reactron says money. This blows Supergirl away. He has all this power and just wants to rob a bank.
As Reactron generates another "crazy star-bomb thing" Supergirl grabs it and shoves it in his head. Then she grabs the power sphere floating above his chest. Reactron is powered down and unconscious.
The people thank Superman and she notices Thomas in the hospital. He's not surprised to see here. His parents aren't too happy with her. It turns out Thomas has brain cancer and the doctors told him he only has weeks to live. Since Supergirl said she wasn't going to let him die, he thinks he has a new lease on life. Superman begins to talk to Thomas to try to set things straight. Supergirl insists that she should do the talking. Thomas tells her that she said he wasn't going to die. Supergirl then says she meant every word. She won't let him die.