Agatha Christie

Words, madmoiselle, are only the outer clothing of ideas.

Agatha Christie (The ABC Murders, 1936)

Imagination is a good servant, and a bad master.

Agatha Christie (The Mysterious Affair at Styles, 1920)

The impossible could not have happened, therefore the impossible must be possible in spite of appearances.

Agatha Christie (Murder on the Orient Express, 1934)