G. K. Chesterton: The Wisdom of Father Brown

6. The Head of Caesar (continued)

"That is true again," said Father Brown, nodding.

"And now, take it from the start. It lies between few people, but at least three. You want one person for suicide; two people for murder; but at least three people for blackmail"

"Why?" asked the priest softly.

"Well, obviously," cried his friend, "there must be one to be exposed; one to threaten exposure; and one at least whom exposure would horrify."

After a long ruminant pause, the priest said: "You miss a logical step. Three persons are needed as ideas. Only two are needed as agents."

"What can you mean?" asked the other.

"Why shouldn't a blackmailer," asked Brown, in a low voice, "threaten his victim with himself? Suppose a wife became a rigid teetotaller in order to frighten her husband into concealing his pub-frequenting, and then wrote him blackmailing letters in another hand, threatening to tell his wife! Why shouldn't it work? Suppose a father forbade a son to gamble and then, following him in a good disguise, threatened the boy with his own sham paternal strictness! Suppose--but, here we are, my friend."

"My God!" cried Flambeau; "you don't mean--"

An active figure ran down the steps of the house and showed under the golden lamplight the unmistakable head that resembled the Roman coin. "Miss Carstairs," said Hawker without ceremony, "wouldn't go in till you came."

"Well," observed Brown confidently, "don't you think it's the best thing she can do to stop outside--with you to look after her? You see, I rather guess you have guessed it all yourself."

"Yes," said the young man, in an undertone, "I guessed on the sands and now I know; that was why I let him fall soft."