Freddie Venton hasn’t seen her old friend, Nasreen Cudmore, in years. But when she learns that Nasreen is a police officer after a chance encounter, Freddie makes a snap decision to follow her when Nasreen gets an urgent callout. Impersonating a forensics officer, Freddie visits Nasreen's crime scene where a man’s body lies slumped over his computer. With the police banned from, and unfamiliar with, social media, it’s Freddie who realizes the victim was a troll and finds @Apollyon: a Twitter account whose profile picture shows the dead body and the missing murder weapon. Time is running out as she and Nasreen face a desperate struggle to catch this cunning, fame-crazed killer --- and to escape their past demons.