'Nothing,' was his brief reply.

'Then why do you come?'

'Merely to corroborate the conclusions I have already arrived at.'

'And might I ask what those conclusions are?'

'Certainly,' replied the detective, with a touch of lassitude in his voice. 'I beg to call your attention, first, to the fact that this train stands between two platforms, and can be entered from either side. Any man familiar with the station for years would be aware of that fact. This shows how Mr. Kipson entered the train just before it started.'

'But the door on this side is locked,' I objected, trying it.

'Of course. But every season ticket-holder carries a key. This accounts for the guard not seeing him, and for the absence of a ticket. Now let me give you some information about the influenza. The patient's temperature rises several degrees above normal, and he has a fever. When the malady has run its course, the temperature falls to three-quarters of a degree below normal. These facts are unknown to you, I imagine, because you are a doctor.'

I admitted such was the case.

'Well, the consequence of this fall in temperature is that the convalescent's mind turns towards thoughts of suicide. Then is the time he should be watched by his friends. Then was the time Mr. Barrie Kipson's friends did not watch him. You remember the 21st, of course. No? It was a most depressing day. Fog all around and mud under foot. Very good. He resolves on suicide. He wishes to be unidentified, if possible, but forgets his season ticket. My experience is that a man about to commit a crime always forgets something.'

'But how do you account for the disappearance of the money?'