Lucy Campbell is the last person you'd expect to hack minds. The college freshman prefers vintage technology, old books and retro fashion. But when she makes a fool of herself in front of her crush, Marco Han, she wishes she could erase the whole episode from his brilliant mind. She's shocked to learn that her older sister, Mollie, can do just that.
Mollie tells Lucy she's found a way to delete people's memories via Spex, the thought-activated successor to smart phones and Google Glass. Yet, when Mollie breaks into Marco's mind, she decides not to erase any embarrassing moments because he already has a crush on Lucy. Encouraged by her sister's discovery, Lucy stops avoiding Marco. Soon, the two are dating, and Marco, a tech guru in his own right, elevates Mollie's mind hacking from a guilty pleasure to an efficient crime-solving tool.
As the three infiltrate more minds, they realize they're not the only ones who can steal memories. Marco suddenly forgets Lucy; and Mollie forgets that she could ever mind hack. Lucy's mind should be safe because she doesn't wear Spex. But then the mysterious hacker, Nick Lethe, comes after her in person.
Lucy flees to the woods, the only place safe from the surveillance of the ubiquitous Spex. If Nick finds her, he'll erase her memories or worse. If she doesn't find him --and stop him -- no one will know that minds can be hacked and lives rewritten.