In her first book of this "series", The Adoration of Jenna Fox, we are introduced to Jenna who isn't quite legal. She was in a horrific car accident that killed her and her two friends. She had ten percent of her brain function which lead scientists (namely her dad) to believe they could upload her essesence and essentially build a new body.
In Fox Inheritance, it is 260 years later. Locke and Kara have new bodies but are being kept prisioner, which they don't realize at first. Kara has hatred for Jenna. She feels that Jenna never tried to save them or help them. Locke just wants to believe what he has is real.