he, the villain and victim of it, the terrible man in the tall
hat, had once crawled up from the sea. For the whole air was dense with
the morbidity of blackmail, which is the most morbid of human things,
because it is a crime concealing a crime; a black plaster on a blacker
wound.

The face of the little Catholic priest, which was commonly complacent
and even comic, had suddenly become knotted with a curious frown. It
was not the blank curiosity of his first innocence. It was rather that
creative curiosity which comes when a man has the beginnings of an idea.
"Say it again, please," he said in a simple, bothered manner; "do you
mean that Todhunter can tie himself up all alone and untie himself all
alone?"

"That is what I mean," said the doctor.

"Jerusalem!" ejaculated Brown suddenly, "I wonder if it could possibly
be that!"

He scuttled across the room rather like a rabbit, and peered with quite
a new impulsiveness into the partially-covered face of the captive. Then
he turned his own rather fatuous face to the company. "Yes, that's it!"
he cried in a certain excitement. "Can't you see it in the man's face?
Why, look at his eyes!"

Both the Professor and the girl followed the direction of his glance.
And though the broad black scarf completely masked the lower half of
Todhunter's visage, they did grow conscious of something struggling and
intense about the upper part of it.

"His eyes do look queer," cried the young woman, strongly moved. "You
brutes; I believe it's hurting him!"

"Not that, I think," said Dr Hood; "the eyes have certainly a singular
expression. But I should interpret those transverse wrinkles as
expressing rather such slight psychological abnormality--"

"Oh, bosh!" cried Father Brown: "can't you see he's laughing?"

"Laughing!" repeated the doctor, with a start; "but what on earth can he
be laughing at?"

"Well," replied the Reverend Brown apologetically, "not to put too fine
a point on it, I think he is laughing at you. And indeed, I'm a little
inclined to laugh at myself, now I know about it."

"Now you know about what?" asked Hood, in some exasperation.

"Now I know," replied the priest, "the profession of Mr Todhunter."

He shuffled about the room, looking at one object after another with
what seemed to be a vacant stare, and then invariably bursting into an
equally vacant laugh, a highly irritating process for those who had to
watch it. He laughed very much over the hat, still