Detective Erika Foster is on a late-night walk near her new house in Blackheath when she stumbles upon the brutal murder of Vicky Clarke, a true-crime podcaster.

Erika is assigned to the case and discovers that Vicky had been working on a new podcast episode about a sexual predator who preys on young female students around South London, staking out his victims in their halls of residence before breaking in at the dead of night. When Erika discovers that Vicky's notes and sound recordings were stolen from her flat at the time of her murder, it leads her to believe that Vicky was close to unmasking the attacker, and she was killed to guarantee her silence.

The case takes on a disturbing twist when the body of a young Bulgarian student doctor is discovered in the same building, and this makes Erika question everything she thought she knew about Vicky. With very little evidence, the clock is ticking to find the killer before he strikes again.