I was thinking. In continuing the tradition of linking the books, is it possible the "gates to hell" are flumes? And the Retros are from Third Earth or Quillan or Veelox after the collapse of Lifelight? And the Second Earth they're on takes place after the Bronx Massacre and the battle with Damon but before the Third Earth where they fought in Soldiers of Halla. I thought Granger was incredibly Saint Dane-like after SYLO. But after STORM, Feit seems more like it. Like the mysterious shadow that flew out of the big plane at the end. Hmmmmm. And that comment about "You could say that" at Fenway when Tucker asks if he's from a different world made me think Third Earth. And it would explain the Ruby. There are ten territories it could have come from. Probably one of the advanced ones. Maybe the Ruby even came from the Blood and that's where the Retros are from. Fun to think about, at least.