This terrifyingly plausible account of the metamorphosis of the perfect nanny into a murderer is really a 'whydunnit' and one I found very, very convincing. The book will, I feel, haunt me for a long time.
As the weeks pass, Louise becomes ever better at being simultaneously invisible and indespensible. Myriam no longer calls to warn her that she's going to be late and Mila no longer asks when Mama is coming home. Louise is there, single-handedly holding up this fragile edifice.