Claudia and Monday have always been inseparable—more sisters than friends. So when Monday doesn’t turn up for the first day of school, Claudia’s worried. When she doesn’t show for the second day, or second week, Claudia knows that something is wrong. Monday wouldn’t just leave her to endure tests and bullies alone. Not after last year’s rumors and not with her grades on the line. Now Claudia needs her best—and only—friend more than ever. But Monday’s mother refuses to give Claudia a straight answer, and Monday’s sister April is even less help.As Claudia digs deeper into her friend’s disappearance, she discovers that no one seems to remember the last time they saw Monday. How can a teenage girl just vanish without anyone noticing that she’s gone?

    Her little brother, Sam, wasn't as lucky. Now she's trying to begin the new life she always dreamed of for them, but never thought she'd have to experience alone. She's hired a techie-genius with a knack for forgery to remove the last ties to her old life. But while she can erase her former identity, she can’t rid herself of the memories. And her troubled history won’t let her ignore the little girl she sees one day in the park. The girl with the bruises and burn marks.That’s when Charlotte begins to receive the messages. Threatening notes left in her apartment--without a trace of entry. And they’re addressed to Piper, her old name. As the messages grow in frequency, she doesn’t just need to uncover who is leaving them; she needs to stop whoever it is before anyone else she loves ends up dead.