Erika Foster, not yet having recovered from the previous investigation, is pulled into the whirlwind of a new case. On a winter morning, a twenty-two-year-old dancer, Marissa, is found on the porch of her own house with her throat cut. Only Foster is capable of digging out the truth and tying together all the threads of this case despite almost complete absence of evidence: the only thing she has is a surveillance camera recording showing that the attacker wore a gas mask. Erika must clearly hurry, because in usually so quiet and peaceful South London, a whole string of brutal murders has already been carried out by a person in the same kind of outfit. But the deeper Erika goes into the investigation, the harder it becomes for her to hold back the onslaught of her own painful memories rooted in the distant past.