A Perfect Getaway lies to its audience

The following paragraph closes out Chapter 1, Part 1 of ‘And Then There Were None’ by Agatha Christie:

“Constance Culmington, he reflected to himself, was exactly the sort of woman who would buy an island and surround herself with mystery. Nodding his head in gentle approval of his logic, Mr. Justice Wargrave allowed his head to nod… He slept…”

Christie was an accomplished mystery writer, and she understood both the importance of leaving clues in the text for the audience to find, and how difficult it was to fool an astute reader. In single point-of-view novels, traditionally told from the POV of the detective this can be relatively simple to accomplish – since the reader doesn’t get access to any of the suspects’ thoughts, anything they say can later turn out to be a lie. It’s more of a challenge when dealing with a multiple POV narrative, when we’re let into the minds of each character, including the killer’s. How do you let the reader know what the killer is thinking without giving away their identity? Hack writers, like Tom Savage, lie, having their characters say, think, and do things they they never would simply to make them more or less suspicious, depending on the need of the story.