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 12.30 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 12.30; 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 in Manderson's bedroom might have been many miles away on the road to Southampton.
I had, however, a pretty good idea already–
