Kayla needs Friday night off, so she switched pizza delivery shifts with Gabie--which means Kayla was the one delivering pizza when the man called. Kayla didn't come back, but she wasn't the one the killer wanted. Gabie knows it should have been her, and she and their coworker Drew are the only ones who still believe that Kayla might be alive. 
 A murder mystery where we see the killer periodically, along with some other people along the way. Could have used fewer POV characters, but still creepy and compulsively readable.