The future world is at peace.Ella Shepherd has dedicated her life to using her unique gift—the ability to enter people's dreams and memories using technology developed by her mother—to help others relive their happy memories.But not all is at it seems.Ella starts seeing impossible things—images of her dead father, warnings of who she cannot trust. Her government recruits her to spy on a rebel group, using her ability to experience—and influence—the memories of traitors. But the leader of the rebels claims they used to be in love—even though Ella's never met him before in her life. Which can only mean one thing...Someone's altered her memory.Ella's gift is enough to overthrow a corrupt government or crush a growing rebel group. She is the key to stopping a war she didn't even know was happening. But if someone else has been inside Ella's head, she cannot trust her own memories, thoughts, or feelings.So who can she trust?