In Agatha Christie's "Third Girl" how exactly does this murder work?

Question

Norma Restarick goes to Poirot saying that she believes she has committed a murder, and has gaps in her memory where she can't remember what she was doing. We later find out that this is because she's been being drugged by two people posing as her father and her stepmother/flatmate. Poirot arranges for her to be 'kidnapped' by a psychiatrist, and he treats her and detoxes her.

The climax of the book comes when she's found, believing she's committed a second murder, having been called back to London by a newspaper advert. The murder has already been committed by her stepmother/flatmate (Frances) — she enters the flat and finds the body. However, the blood is already congealing, leading Poirot to know that she can't have been the one to kill him. Frances then comes in to discover the 'scene of the crime'.

What I'm struggling to understand is that Norma hasn't taken any drugs for quite a while at this point, and as far as I can remember, doesn't meet Frances before she goes into the flat. At what point does Frances drug her again, resulting in the loss of memory etc.?

Answer 1

As far as I can tell, Norma was not drugged at the time that she discovered David's body. Rather, Frances depended on the earlier effects of the drugs, and Norma assuming that she'd had another fugue state. Even if Norma claimed that she'd just walked in and found the body, there were earlier statements of her having had lapses in her memory, and of her suspecting that she had killed one person (Louise) and attempted to kill another (Mary), so no one would believe her saying she just walked in on the murder. As it is, Norma is in such shock that she picks the knife up, making her look all the more guilty were it not for the clue that the blood had already dried.