The Phantom Zone - an otherdimensional prison for Krypton's worst criminals.
Something is going wrong, and it requires Superman to head into that prison to seek out the problem. Trouble is, as we saw in the first issue, Kal-El doesn't have his powers anymore, and that makes the rest of the Justice League nervous.
Check out Crave Online's exclusive preview of Batman Beyond Universe #2, the only place where the pre-New 52 continuity still exists (besides our hearts and minds), and Billy Batson is still called Captain Marvel. Thank you, Christos Gage and Iban Coello.