"My suspicion is shared by another, whose mind it has entered by a different channel."
"Who is this other?"
"Your son!"
"What do you say? Leon suspects that I have committed a crime? This is terrible! But why? Why, in the name of heaven, should he harbor such a thought against me?" The Doctor was unusually excited.
"He saw you take the culture tube, containing the bacillus, out of the laboratory."
"You say Leon saw me take a culture tube from the laboratory?" The Doctor spoke the words separately, with a pause between each, as though stung by the thought which they conveyed. Mr. Barnes merely nodded assent.
"Then the end is at hand!" muttered the Doctor, softly. "All is ready for the final experiment!" Mr. Barnes did not comprehend the meaning of what he heard, but, as the Doctor walked about the room, back and forth, like a caged animal, seemingly oblivious of the fact that he was not alone, the detective thought it wise to observe him closely lest he might attack him unawares.
Presently the Doctor stopped before the detective, and thus addressed him, in calm tones:
"Mr. Barnes, you are shrewd and you are clever. You have guessed a part of the truth, and I have decided to tell you everything."
"I warn you," said Mr. Barnes, quickly, "that what you say will be used against you."