is way to mention Southampton openly to two persons. _He
even went so far as to ring up a hotel at Southampton and ask questions
which bore out Marlowe's story of his errand._ This was the call he was
busy with when Martin was in the library.

Now let us consider the alibi. If Manderson was in the house that night,
and if he did not leave it until some time after twelve-thirty, Marlowe
could not by any possibility have had a direct hand in the murder. It is
a question of the distance between Marlstone and Southampton. If he had
left Marlstone in the car at the hour when he is supposed to have done
so--between ten and ten-thirty--with a message from Manderson, the run
would be quite an easy one to do in the time. But it would be physically
impossible for the car--a fifteen horse-power four-cylinder
Northumberland, an average medium-power car--to get to Southampton by
half-past six unless it left Marlstone by midnight at latest. Motorists
who will examine the road-map and make the calculations required, as I
did in Manderson's library that day, will agree that on the facts as
they appeared there was absolutely no case against Marlowe.

But even if they were not as they appeared; if Manderson was dead by
eleven o'clock, and if at about that time Marlowe impersonated him at
White Gables; if Marlowe retired to Manderson's bedroom--how can all
this be reconciled with his appearance next morning at Southampton? _He
had to get out of the house, unseen and unheard, and away in the car by
midnight._ And Martin, the sharp-eared Martin, was sitting up until
twelve-thirty in his pantry, with the door open, listening for the
telephone bell. Practically he was standing sentry over the foot of the
staircase, the only staircase leading down from the bedroom floor.

With this difficulty we arrive at the last and crucial phase of my
investigation. Having the foregoing points clearly in mind, I spent the
rest of the day before the inquest in talking to various persons and in
going over my story, testing it link by link. I could only find the one
weakness which seemed to be involved in Martin's sitting up until
twelve-thirty; and since his having been instructed to do so was
certainly a part of the plan, meant to clinch the alibi for Marlowe, I
knew there must be an explanation somewhere. If I could not find that
explanation my theory was valueless. I must be able to show that at the
time Martin went up to bed, the man who had shut himself