Vee Bell is certain of one irrefutable truth—her sister's friend Sophie didn't kill herself. She was murdered.

Vee knows this because she was there. Everyone believes Vee is narcoleptic, but she doesn't actually fall asleep during these episodes: When she passes out, she slides into somebody else's mind and experiences the world through that person's eyes. She's slid into her sister as she cheated on a math test, into a teacher sneaking a drink before class. She learned the worst about a supposed "friend" when she slid into her during a school dance. But nothing could have prepared Vee for what happens one October night when she slides into the mind of someone holding a bloody knife, standing over Sophie's slashed body.

Vee desperately wishes she could share her secret, but who would believe her? It sounds so crazy that she can't bring herself to tell her best friend, Rollins, let alone the police. Even if she could confide in Rollins, he has been acting distant lately, especially now that she's been spending more time with Zane.

Enmeshed in a terrifying web of secrets, lies, and danger and with no one to turn to, Vee must find a way to unmask the killer before he or she strikes again.