3 He can change his appearance easily.
4 He studied medicine. He could easily cut up a body in the dark.
5 He knows the lanes and yards of Whitechapel well.
6 He can escape from the police because he knows their plans - indeed, he makes their plans.
The arguments against:
1 He spends his life fighting crime.
2 I know my friend. I know he could not do these things.
When I read what I had written, I began to wonder how well I knew Holmes. Did he really fight against crime? He took cases because they interested him, not because he hated crime. It was all just a game to him. He fought crime to amuse himself. It was now late at night. I was terribly tired, but I knew that I had to decide what to do before Holmes came back. Suddenly, as I lay back in my chair, half-asleep, the terrible picture of Holmes cutting up that girl's body appeared again before my eyes. Then, finally, I knew. It was not what I had seen him do, but how he had done it. That look of cool amusement on his face. The way he sang as he worked. The man who could do that could do anything.
Next day I packed my bags and moved into a hotel. That evening I asked Mary to have dinner with me. I told her that I could not sleep while she lived alone in London and the Whitechapel murderer was free to kill again. I asked her to marry me sooner than we had planned. She laughed and said she was not afraid of the murderer. He never killed women like her. But she would marry me as soon as possible, she said, because I looked so worried and unhappy.
Then I wrote a letter to Holmes.
'I am sorry that I cannot welcome you home,' I wrote, 'but I have a reason for that, the best reason in the world. Mary and I are married. She was badly frightened by those awful murders in Whitechapel and will feel safer now that I am by her side.
'It is wonderful to hear from you that Professor Moriarty is dead. Of course I look forward to hearing the full story of his death from you.
'Mary and I are spending a little time travelling. Please write to me at my London club.'
Several days later, Mary and I were married, and we left London. In a quiet little town by the sea, with Mary by my side, I felt strong enough to face the
awful truth about Holmes, and to think about what I had to do. I could not go to the police with my story. They would think that I was mad. I decided that I would have to watch Holmes carefully. Only I could stop him killing again.
When I returned to London, I found a letter from Holmes waiting for me at my club. He told me that he was going to Russia, to work on a strange and exciting murder case.
'I am bored with London, now that Jack the Ripper is dead,' he wrote. 'Perhaps the foreign criminal has more to offer me. I shall not return to London for some time. Please inform me of your new address.'
After reading this, I was happier than I had been for many weeks. Mary and I finished our holiday and moved to a house in London, not far from Baker Street. I was busy with my work as a doctor, and we lived quietly and happily together.
During this time I was sent two wonderful letters by Holmes.
He had brought his work on the Russian mystery to a successful end, and had gone from Russia to Ceylon, where the sudden death of a rich tea-planter offered him the interest and excitement he needed. The Holmes who wrote these letters to me sounded like the old Holmes that I knew.
'He is dangerous when he is bored and uses cocaine,' I thought. 'When he is enjoying his work, London is safe.'
One day in March, as I walked along Baker Street, I saw a light in Holmes's window, and knew that he had returned. I went in, and he welcomed me like the dear old friend he had been. All evening we sat by the fire, and he told me everything that had happened in Russia and Ceylon. But what I really wanted to hear about was Moriarty's death, and about that he said not one word.
At last I could wait no longer.
'My dear Holmes,' I said. 'It is almost midnight, and you still have not told me how Moriarty died!'
At once his face went white, and his eyes became fixed in a stare. He sat silent and unmoving, as the seconds passed.
Then he said, 'I'm sorry, Watson. I was thinking about something to do with my last case. What did you say?' 'Moriarty,' I repeated. 'You have not told me how he died.' 'He has gone,' he said. 'That is all that anyone needs to know about him.'