An advertising executive is found murdered in her luxury London apartment. DI Nash and DS Moretti quickly exhaust the obvious leads when a near identical killing occurs.

Though joined in death, initially the only other connection between the two victims is the cat videos on their social media accounts. Following this tenuous thread, the detectives form a profile of the killer.

With Nash drawn away from the case on covert police work, Moretti does his best to bring in a suspect. But suspicions develop in the team when he discovers a direct communication between Nash herself and both victims.

If it comes to it, will Nash blow her cover to catch a killer?