Detective Petra Connor is struggling with a baffling drive-past murder when Isaac Gomez, a young research prodigy, tells her he's found something she might want to see. His theory that there's a connection between six unsolved murders committed in the LAPD area over the past six years, all at around midnight on June 28, seems fanciful at first - but soon the links become clearer.

Something evil has managed to conceal itself between the dry pages of the files: a series of killings so meticulously constructed that the mind behind them would have remained invisible without Isaac's sharp probing. And June 28 is just a month away - will Petra be able to stop the murderer from striking again?