The Nanny belongs to a strain of British crime writing that keeps its horrors indoors. Heather Burnside works the domestic thriller, where the threat is not a stranger in an alley but somebody invited in, trusted with the children and handed a key to the front door.
The appeal of the form is its ordinariness. Everything that goes wrong could plausibly go wrong in any household, which is what gives the genre its grip, and the writing here is built for momentum rather than atmosphere: short chapters, steady escalation, and a plot that keeps a firm hand on the listener’s suspicions.