the warden, with a chuckle. 'Plan of escape number one has gone wrong.' Then, as an afterthought: 'But why did he address it to Dr Ransome?'
  'And where did he get the pen and ink to write with?' asked the guard.
  The warden looked at the guard and the guard looked at the warden. There was no apparent solution of that mystery. The warden studied the writing carefully, then shook his head.
  'Well, let's see what he was going to say to Dr Ransome,' he said at length, still puzzled, and he unrolled the inner piece of linen.
  'Well, if that â what â what do you think of that?' he asked, dazed.
  The guard took the bit of linen and read this:
  'Epa cseot d'net niiy awe htto n'si sih. T.'
III
The warden spent an hour wondering what sort of a cipher it was, and half an hour wondering why his prisoner should attempt to communicate with Dr Ransome, who was the cause of him being there. After this the warden devoted some thought to the question of where the prisoner got writing materials, and what sort of writing materials he had. With the idea of illuminating this point, he examined the linen again. It was a torn part of a white shirt and had ragged edges.
  Now it was possible to account for the linen, but what the prisoner had used to write with was another matter. The warden knew it would have been impossible for him to have either pen or pencil, and, besides, neither pen nor pencil had been used in this writing. What, then? The warden decided to personally investigate. The Thinking Machine was his prisoner; he had orders to hold his prisoners; if this one sought to escape by sending cipher messages to persons outside, he would stop it, as he would have stopped it in the case of any other prisoner.
  The warden went back to Cell 13 and found The Thinking Machine on his hands and knees on the floor, engaged in nothing more alarming than catching rats. The prisoner heard the warden's step and turned to him quickly.
  'It's disgraceful,' he snapped, 'these rats. There are scores of them.'
  'Other men have been able to stand them,' said the warden. 'Here is another shirt for you â let me have the one you have on.'
  'Why?' demanded The Thinking Machine, quickly. His tone was hardly natural, his manner suggested actual perturbation.
  'You have attempted to communicate with Dr Ransome,' said the warden severely. 'As my prisoner, it is my duty to put a stop to it.'
  The Thinking Machine was silent for a moment.
  'All right,' he said, finally. 'Do your duty.'
  The warden smiled grimly. The prisoner arose from the floor and removed the white shirt, putting on instead a striped convict shirt the warden had brought. The warden took the white shirt eagerly, and then and there compared the pieces of linen on which was written the cipher with certain torn places in the shirt. The Thinking Machine looked on curiously.
  'The guard brought you those, then?' he asked.
  'He certainly did,' replied the warden triumphantly. 'And that ends your first attempt to escape.'
  The Thinking Machine watched the warden as he, by comparison, established to his own satisfaction that only two pieces of linen had been torn from the white shirt.
  'What did you write this with?' demanded the warden.
  'I should think it a part of your duty to find out,' said The Thinking Machine, irritably.
  The warden started to say some harsh things, then restrained himself and made a minute search of the cell and of the prisoner instead. He found absolutely nothing; not even a match or toothpick which might have been used for a pen. The same mystery surrounded the fluid with which the cipher had been written. Although the warden left Cell 13 visibly annoyed, he took the torn shirt in triumph.
  'Well, writing notes on a shirt won't get him out, that's certain,' he told himself with some