But then again, as Prelice further argued, while the train drew near to the coast, Mrs. Rover must have known that in murdering Agstone she was not only securing the freedom of Mona Chent, whom she hated, but also was placing her lover in a dangerous position. Agstone was a necessary witness for the prosecution, whom Shepworth of all men did not wish to see placed in the box, so the supposition would be, were the man found dead in Number Forty, that Shepworth had killed him to save Mona Chent. As a matter of fact, this is exactly what had taken place, and in saving Ned from the sailor's knife Mrs. Rover, always presuming that she was guilty, had simply condemned her lover to a death on the scaffold. But that Prelice had been clever enough to admit the crowd of guests, so that all might see the barrister's helpless position, it is certain that the man would have been arrested, and probably sentenced to death, since it would have been extraordinarily difficult for him to clear his character in the face of circumstances. Therefore on these assumptions, for that they were and no more, Prelice after much reflection decided that Mrs. Rover was innocent. Finally, the young man recollected that a woman dressed as described, by Ned, and in the costume which Mrs. Rover confessed to wearing, had passed down the stairs while he was waiting for entrance to Number Forty and immediately before the discovery of the crime. She could scarcely have been Mrs. Rover, for as that lady could have easily proved an _alibi_ by returning to her guests and casually unmasking at the right moment, it would have been useless for her to leave the mansions. Of course, the lady--whether Mrs. Rover or a stranger--certainly might have followed Prelice down to the door, knowing that he would be certain to discover the tragedy, and might merely have descended to return to the ballroom overhead when the young man entered Shepworth's flat. But then, again, the person in question could not have known that Prelice, masked and unknown, was going to enter Number Forty, so there would be no reason to track him there. And to conclude, the murderess--if a woman was guilty--must have known that Shepworth, being in a cataleptic state, must have seen and remembered her very peculiar frock.