Plenty of teenagers feel invisible. Fiona McClean actually is. An invisible girl is a priceless weapon. Fiona’s own father has been forcing her to do his dirty work for years—everything from spying on people to stealing cars to breaking into bank vaults. After sixteen years, Fiona’s had enough. She and her mother flee to a small town, and for the first time in her life, Fiona feels like a normal life is within reach. But Fiona’s father isn’t giving up that easily. Of course, he should know better than anyone: never underestimate an invisible girl.

Three months after Fiona escapes from her father's syndicate, all seems well in her tiny town of Madison, Arizona. She and Seth are happy together - apart from the teensy fact of Fiona being jealous that Seth can see through her invisibility - and her family and friends are safe. But when the local syndicate and even the Army show up, it's clear there's more going on in town than she could ever imagine. It seems like these huge powers are interested in the old Radiasure factory - could they be reproducing the infamous drug that caused mutations? - and everyone suspects Fiona of knowing more than she should. As Fiona and her friends try to cover their tracks, they discover that they do have some dangerous knowledge. Though at first determined to stop anyone from remaking Radiasure, Fiona learns a secret that could change everything, including her invisibility. Torn between her own desires and the greater good, Fiona might be too blindsided to see the real villain coming.