Page:The Sign of Four.pdf/28

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THE SCIENCE OF DEDUCTION.
19

to my lens on the inside of this case. Inference—that your brother was often at low water. Secondary inference—that he had occasional bursts of prosperity, or he could not have redeemed the pledge. Finally, I ask you to look at the inner plate, which contains the keyhole. Look at the thousands of scratches all round the hole—marks where the key has slipped. What sober man's key could have scored those grooves? But you will never see a drunkard's watch without them. He winds it at night, and he leaves these traces of his unsteady hand. Where is the mystery in all this?'

'It is as clear as daylight,' I answered. 'I regret the injustice which I did you. I should have had more faith in your marvellous faculty. May I ask whether you have any professional inquiry on foot at present?'

'None. Hence the cocaine. I cannot live without brain-work. What else is there