But he had known when to stop. The worst part of the enterprise was before him, the business--clearly of such vital importance to him, for whatever reason--of shutting himself in Manderson's room and preparing a mass of convincing evidence of its having been occupied by Manderson; and this with the risk--very slight, as no doubt he understood, but how unnerving!--of the woman on the other side of the half-open door awaking and somehow discovering him. True, if he kept out of her limited field of vision from the bed, she could only see him by getting up and going to the door. I found that to a person lying in her bed, which stood with its head to the wall a little beyond the door, nothing was visible through the doorway but one of the cupboards by Manderson's bed-head. Moreover, since this man knew the ways of the household, he would think it most likely that Mrs. Manderson was asleep. Another point with him, I guessed, might have been the estrangement between the husband and wife, which they had tried to cloak by keeping up, among other things, their usual practice of sleeping in connected rooms, but which was well known to all who had anything to do with them. He would hope from this that if Mrs. Manderson heard him, she would take no notice of the supposed presence of her husband. So, pursuing my hypothesis, I followed the unknown up to the bedroom, and saw him setting about his work. And it was with a catch in my own breath that I thought of the hideous shock with which he must have heard the sound of all others he was dreading most: the drowsy voice from the adjoining room. What Mrs. Manderson actually said, she was unable to recollect at the inquest. She thinks she asked her supposed husband whether he had had a good run in the car. And now what does the unknown do? Here, I think, we come to a supremely significant point. Not only does he--standing rigid there, as I picture him, before the dressing-table, listening to the sound of his own leaping heart--not only does he answer the lady in the voice of Manderson; he volunteers an explanatory statement. He tells her that he has, on a sudden inspiration, sent Marlowe in the car to Southampton; that he has sent him to bring back some important information from a man leaving for Paris by the steamboat that morning. Why these details from a man who had long been uncommunicative to his wife, and that upon a point scarcely likely to interest her? Why these details _about Marlowe_?