Nocebo

Nocebo is the episode where the killer and the police are doing the same thing, and the title tells you why. A nocebo is a harmful effect produced by expectation rather than by any physical cause, and the film's offender has no weapon beyond suggestion. Two children are found dead with the signs of a ritual killing, and Alex Fielding is disturbed both by the deaths and by the lack of care shown by the children's families — a reaction that is also her own problem, since she is struggling with her son Ben.

The investigation leads to three separate strands: a property tycoon willing to do anything to get rent paid, a preacher whose healing activities involve animal sacrifice, and an artist who paints in blood. The police find a laboratory with evidence of sacrifice and blood paintings. Hill cannot tell whether this is a cult, or whether there are two offenders with one following the other, and the bodies may be a warning rather than the crime itself.

The film's most effective move is the one that turns it personal. Fielding had taken Hill's advice and hired a nanny, which eased the pressure between her work and Ben. Then the nanny comes home without him, and the team understands that the killer has been nearby and unseen throughout, manipulating the investigation by psychological suggestion exactly as they manipulated their victims. The killer has Ben. It is the closest the Lahbib run comes to the threat level of Torment, and it works because the danger to the child arrives through a decision Fielding made on Hill's recommendation.

That gives the episode its real subject: the cost of trusting the psychologist's judgement. Hill's advice was sensible and it put a child in reach of a killer, and the show does not pretend otherwise or resolve the tension with an apology. The reversal is also a nice piece of plotting — the nanny was hired to reduce risk and became the mechanism of it.

What the episode does badly is the curse. Paula McIntyre and Kevin Geoffries finding themselves under the influence of one is the most anomalous material in the fifth series, and it strains a show whose whole position is that psychological effects have psychological causes. Hill's scepticism about the killer's claimed abilities is the correct note, but the surrounding material has already played the idea for atmosphere.

It drew 5.01 million viewers, the lowest of the series. That is a fair reflection of its problems rather than of its ambitions — the child-in-jeopardy structure is genuinely strong and the resolution lands, but the middle third spends a lot of its time on three suspects who are established as insufficiently interesting to be the answer. The film's best quality is that it makes Fielding's domestic life the vulnerability rather than the sanctuary, which the show would return to.