Supergirl has been out of the hospital after her injuries on a case with the Outsiders. She hasn't contacted Boomer (Captain Boomerang) with whom she had a close friendship. Boomer is drinking away his sorrows at a bar telling his story to someone that bears a strong resemblance to Cassandra Cain, Batgirl.
Kara, Supergirl, has been spending more and more time with Powerboy. They have become closer and closer and more intimate.
In a hidden lair of the League of Assassins, Cassandra Cain is discussing her "tests" against Supergirl with her client. She plans on ending things that night.
At Supergirl's apartment, she tells Powerboy that in order to find who's trying to kill her, she needs to go someplace on her own. Powerboy isn't too happy with that. He almost seems possesive of her.
Supergirl goes to the Batcave and uses their computer. Robin tells her she can't just come in and use it whenever she wants. Supergirl asks for information on Cassandra and the League of Assassins. Robin says she's the only person to ever have hurt Bruce, which makes her the most dangerous person on the planet.
Kara sets off to confront the League. She continues to have flashbacks of her father seemingly experimenting on her, telling her that she's special. Cassandra was ready for her. Using diamond dust, red wavelength uvb lights, and dressed in her Batgirl guise, Cassandra attacls Supergirl.
During the fight, she sees Boomer chained and beaten, hanging above her. Cassandra takes that moment to slash her stomache with a special sword. Grabbing her from behind, Supergirl and Batgirl are both surprised when some crystal-like blades pop out of Supergirls back (and stomache wound) into Batgirl's shoulder and side. Kara places a call to Powerboy to help her with Boomer and Powerboys obsession is seen.