- Aliens have arrived on Earth-16!
- Superboy and five Justice Leaguers have been abducted!
- Metropolis is in danger!
- Enter: Brainiac
The comic issue has been on sale since October 17th, 2012. If you don't have a local comic store near you, here are the websites I recommend buying from online and online internationally, http://yjcave.blogspot.com/2011/10/buying-young-justice-comics-online.html.
Sneak Peak Photos from issue #21