Delta Paradox — Ken Warner

After the failed attempt to return to their own universe, Malia and Jaden must find Ezra James--the only person in this world with the knowledge they need to find their way home. But when he discovers that they didn't arrive here the way they thought they had, they realize they're going to need more help than he alone can provide. Finding the solution embroils them in a world war, and before long, they learn that a previously unknown Axis leader possesses the secret they need to get home.Meanwhile, the Collective is on the run with nowhere to turn after the Malor destroy their complex in Fiji, counting on the success of their erstwhile enemies' desperate mission to save the planet.