When the official moved away, I asked my friend what he expected to
find in the carriage that would cast any light on the case.

"Nothing," was his brief reply.

"Then why do you come?"

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

"And may 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.