“I have looked at all the knots on Mr Todhunter,” reiterated Hood quietly. “I happen to know something about knots; they are quite a branch of criminal science. Every one of those knots he has made himself and could loosen himself; not one of them would have been made by an enemy really trying to pinion him. The whole of this affair of the ropes is a clever fake, to make us think him the victim of the struggle instead of the wretched Glass, whose corpse may be hidden in the garden or stuffed up the chimney.” There was a rather depressed silence; the room was darkening, the sea-blighted boughs of the garden trees looked leaner and blacker than ever, yet they seemed to have come nearer to the window. One could almost fancy they were sea-monsters like krakens or cuttlefish, writhing polypi who had crawled up from the sea to see the end of this tragedy, even as 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.