For 13-year-old Jack, things are going from bad to worse to horrible.

First, his parents go missing and he is forced to move across the country away from everything and everyone he knows.

And just as he makes a new friend, the two of them fall through a crack in the earth into a below-ground alien world full of Inner Terrestrials, or ITs for short.

Stuck below ground and confined, Jack is schooled about the ITs: their history (they came here thousands of years ago); their real name (the Bennots); their former planet (Helios V); and their mortal enemy (the Malzoyans).

The ITs/Bennots keep him alive, but he's got to be watched. And who's going to watch him? A human girl, Jen, brought down to the ITs' world as a toddler. A bit hairy and a lot smelly, Jen knows little about humans.

The good news is that Jack is finally allowed out to see the Bennot world, which is full of things that don't seem possible underground: huge lakes, factories, green farms, sunlit skies, and a bustling city. And unbelievable dangers.

And, as it turns out, a hidden cyborg army called the Gireens, copies of Earth's fiercest soldiers from the ages. The problem is, they have never been tested or used.

But now, the megalomaniac Malzoyans have found the Bennots, and, speeding toward Earth from the dying Helios V, they intend to exterminate all that remain. Oh yeah, along with everyone else on the planet.

Can Jack and Jen unlock the cyborg army and save themselves, the Bennots...and humanity...from extinction?