When we encounter Emily Brent at work with her diary, why would she write down THE MURDERER'S NAME IS BEATRICE TAYLOR? Why would she write that down?
Agatha Christie's classic mystery novel, "And Then There Were None," is a version of the "locked room" type of mystery. A group of people gather at an island home, only to be cut off from the mainland by a storm. When the guests begin dying, they must discover which of them is the murderer.
The novel is also a study in human psychology. Each person trapped on the island is accused of a murder that went unsolved, either because it appeared to be accidental, or because there was no hard evidence. They each deal with the rising level of guilt and fear in different ways, according to their personality types.
Miss Brent is a perfect lady, very proper in her demeanor and with a severe morality that would seem to exclude murderous tendencies. However, she did at one time refuse help to Beatrice Taylor, a girl pregnant out of wedlock, and now someone believes that that girl's suicide is on her hands. But the important thing to note is that Miss Brent doesn't think she's done anything wrong. On the surface, she is calm, collected, and above suspicion. She has suppressed the guilt to such an extent that it only appears in this moment, when she goes into a sort of trance while writing in her diary. A very deep and unknown part of her believes that the ghost of Beatrice is back for vengeance.