I would first draw attention to one important fact. _The only person who professed to have heard Manderson mention Southampton at all before he started in the car was Marlowe._ His story--confirmed to some extent by what the butler overheard--was that the journey was all arranged in a private talk before they set out, and he could not say, when I put the question to him, why Manderson should have concealed his intentions by giving out that he was going with Marlowe for a moonlight drive. This point, however, attracted no attention. Marlowe had an absolutely air-tight alibi in his presence at Southampton by six-thirty; nobody thought of him in connection with a murder which must have been committed after twelve-thirty--the hour at which Martin, the butler, had gone to bed. But it was the Manderson who came back from the drive who went out of his 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.