Where did you get into the train?"

The two passengers looked at one another in astonishment.

"What a dreadful thing!" one of them exclaimed. "Why, sir, to-night,
while my friend here and I were asleep, one of our fellow-travellers did
disappear. I made a remark about it, but this gentleman very reasonably
pointed out that he must have got out at some station while we were
asleep."

The official was keenly interested.

"What was this passenger like?"

"Quite easily recognised, sir; a man of about sixty, rather stout, and
wearing whiskers."

"That tallies with the description. Might he have been a butler or a
steward?"

"That is exactly what he looked like."

"Then that must be the man whose body has been found upon the line. But
I do not know whether it is to be regarded as a case of suicide or of
murder, for some hand baggage has been picked up as well: a suicide
would not have thrown his luggage out, and a thief would not have wanted
to get rid of it."

The passenger who had not yet spoken, broke in.

"You are wrong, sir; at any rate all his luggage was not thrown on to
the line," and he pointed to the bundle left upon the seat. "I thought
that belonged to the gentleman here, but he has just told me it isn't
his."

The official rapidly unfastened the straps and started back.

"Hullo! A bottle of liquid carbonic acid! Now what does that mean?" He
looked at it. "Did this bundle belong to the man who disappeared?"

The two passengers shook their heads.

"I don't think so," one of them said; "I should certainly have noticed
that Scotch rug; but I did not see it."

"Then there was a fourth passenger in this compartment?" the official
enquired.

"No, we travelled alone," said one of the men, but the other dissented.

"It is very odd, and I am not sure about it, but I really am wondering
whether someone did not get into our compartment last night while we
were asleep. I have a vague impression that someone did, but I can't be
sure."

"Do try to remember, sir," the official urged him; "it is of the very
highest importance."

But the passenger shook his shoulders doubtfully.

"No, I really can't say anything definite; and, besides, I have a
shocking headache."

The official was silent for a minute or two.

"In my opinion, gentlemen, you have been uncommonly lucky to escape
murder yourselves. I do not quite understand yet how the murder was
done, but I incline to think it proves almost incredible