In his introduction to Patricia Highsmith’s first collection of short stories, Eleven (published in 1970), Graham Greene vividly describes the particular quality of her writing. ‘She is,’ he says, ‘a writer who has created a world of her own – a world claustrophobic and irrational which we enter each time with a sense of personal danger … even with a certain reluctance, for these are cruel pleasures we are going to experience… ‘He goes on: ‘It is not the world as we once believed we knew it, but it is frighteningly more real to us than the house next door.’

This sense of personal danger brought on by an agony of suspense is at its most acute ever in Ms Highsmith’s new book, People Who Knock on the Door. And we experience a more refined frisson because the level of physical violence in the book is very low; its violence