The next day Father Brown came in rather wearily, and threw down his black bundle of an umbrella with the air of a pilgrim laying down his staff. He had an air of some depression. But it was as it was so often in his criminal investigations. It was not the depression of failure, but the depression of success.
"It's rather a shock," he said in a dull voice; "but I ought to have guessed it. I ought to have guessed it when I first went in and saw the thing standing there."
"When you saw what?" asked Granby impatiently.
"When I saw there was only one suit of armour," answered Father Brown. There was a silence during which the lawyer only stared at his friend, and then the friend resumed.
"Only the other day I was just going to tell my niece that there are two types of men who can laugh when they are alone. One might almost say the man who does it is either very good or very bad. You see, he is either confiding the joke to God or confiding it to the Devil. But anyhow he has an inner life. Well, there really is a kind of man who confides the joke to the Devil. He does not mind if nobody sees the joke; if nobody can safely be allowed even to know the joke. The joke is enough in itself, if it is sufficiently sinister and malignant."
"But what are you talking about?" demanded Granby. "Whom are you talking about? Which of them, I mean? Who is this person who is having a sinister joke with his Satanic Majesty?"
Father Brown looked across at him with a ghastly smile.
"Ah," he said, "that's the joke."
There was another silence, but this time the silence seemed to be rather full and oppressive than merely empty; it seemed to settle down on them like the twilight that was gradually turning from dusk to dark. Father Brown went on speaking in a level voice, sitting stolidly with his elbows on the table.
"I've been locking up the Musgrave family," he said. "They are vigorous and long-lived stock, and even in the ordinary way I should think you would wait a good time for your money."