Out There: Book Four: Earth

When Sami, Alejandro and Brian rematerialize in Paradise, Arizona...no one is there. The worsening planet-wide water shortages have forced everyone to pack themselves into the major cities. The three friends trek across the desert to Phoenix to find Sami's mother, to search for Brian’s parents, and to warn the world that the TakTi are coming.
It’s hell in Phoenix.
Worse, they soon discover that KetaNim is already there. He is helping the demagogue, Todd Rover, become president of the United States and, so, pave the way to TakTi colonization. To make matters worse, SimSimKeta and her forces are arriving near the planet Jupiter. And SimSim is holding Sami’s father as a hostage to prevent her from meddling.
Sami, Alejandro, Brian and their new friends (a gang of kids living in an abandoned underground station they call "Timbuktu") must do something about all of this. And they have only hours in which to do it.
It will take everything Sami has learned from her experiences with the Adonae, the TakTi, and the Svaash to free Brian’s parents, to save her father, and maybe, just maybe, stop a global catastrophe.