Silence held them all up again, and then the doctor said rather sulkily:  “Well, I may be wrong; there are objections to everything.  But I stick to the main point.  No man but an idiot would pick up that little hammer if he could use a big hammer.”

With that the lean and quivering hands of Wilfred Bohun went up to his head and seemed to clutch his scanty yellow hair.  After an instant they dropped, and he cried:  “That was the word I wanted; you have said the word.”

Then he continued, mastering his discomposure:  “The words you said were, `No man but an idiot would pick up the small hammer.’”

“Yes,” said the doctor.  “Well?”

“Well,” said the curate, “no man but an idiot did.”  The rest stared at him with eyes arrested and riveted, and he went on in a febrile and feminine agitation.

“I am a priest,” he cried unsteadily, “and a priest should be no shedder of blood.  I—­I mean that he should bring no one to the gallows.  And I thank God that I see the criminal clearly now —­because he is a criminal who cannot be brought to the gallows.”

“You will not denounce him?” inquired the doctor.

“He would not be hanged if I did denounce him,” answered Wilfred with a wild but curiously happy smile.  “When I went into the church this morning I found a madman praying there—­that poor Joe, who has been wrong all his life.  God knows what he prayed; but with such strange folk it is not incredible to suppose that their prayers are all upside down.  Very likely a lunatic would pray before killing a man.  When I last saw poor Joe he was with my brother.  My brother was mocking him.”

“By Jove!” cried the doctor, “this is talking at last.  But how do you explain—­”

The Rev. Wilfred was almost trembling with the excitement of his own glimpse of the truth.  “Don’t you see; don’t you see,” he cried feverishly; “that is the only theory that covers both the queer things, that answers both the riddles.  The two riddles are the little hammer and the big blow.  The smith might have struck the big blow, but would not have chosen the little hammer.  His wife would have chosen the little hammer, but she could not have struck the big blow.  But the madman might have done both.  As for the little hammer—­why, he was mad and might have picked up anything.  And for the big blow, have you never heard, doctor, that a maniac in his paroxysm may have the strength of ten men?”

The doctor drew a deep breath and then said, “By golly, I believe you’ve got it.”

Father Brown had fixed his eyes on the speaker so long and steadily as to prove that his large grey, ox-like eyes were not quite so insignificant as the rest of his face.  When silence had fallen he said with marked respect:  “Mr. Bohun, yours is the only theory yet propounded which holds water every way and is essentially unassailable.  I think, therefore, that you deserve to be told, on my positive knowledge, that it is not the true one.”  And with that the old little man walked away and stared again at the hammer.