Supergirl and Superman must work together to defeat the nuclear menace of Reactron! But when Superman tries to teach her the hardest lesson of all, he learns that Supergirl has something to teach him! And wait until you see the startling new direction the book takes!
Kara is dealing with getting all of her Krypton memories back. She keeps seeing all her friends and the destruction of Krypton. Superman tries to talk to her. She says she feels they're there for a bigger reason. Superman is called away (to save a cat in a tree) before they can talk further.
Supergirl is then attacked. She is knocked from space into the ocean. A man in a star patterned suit hits her with a nuclear blast. She returns to get him. Prepared, she easily deflects all his blows. She wants to know who he is. He tells her to just apprehend him and take him to STAR Labs or something. They keep fighting and Kara keeps trying to find out who he is. Finally, he tells her his name is Reactron and shows her the full extent of his powers.