“I’m sure you wouldn’t,” laughed Antony. “Well, we can have a look when we go in. If the other keys are outside, then this one was probably outside too, and in that case—well, it makes it more interesting.”
Cayley said nothing. Bill chewed a piece of grass, and then said, “Does it make much difference?”
“It makes it more hard to understand what happened in there. Take your accidental theory and see where you get to. No instinctive turning of the key now, is there? He’s got to open the door to get it, and opening the door means showing his head to anybody in the hall—his cousin, for instance, whom he left there two minutes ago. Is a man in Mark’s state of mind, frightened to death lest he should be found with the body, going to do anything so foolhardy as that?”
“He needn’t have been afraid of me,” said Cayley.
“Then why didn’t he call for you? He knew you were about. You could have advised him; Heaven knows he wanted advice. But the whole theory of Mark’s escape is that he was afraid of you and of everybody else, and that he had no other idea but to get out of the room himself, and prevent you or the servants from coming into it. If the key had been on the inside, he would probably have locked the door. If it were on the outside, he almost certainly wouldn’t.”
“Yes, I expect you’re right,” said Bill thoughtfully. “Unless he took the key in with him, and locked the door at once.”
“Exactly. But in that case you have to build up a new theory entirely.”
“You mean that it makes it seem more deliberate?”
“Yes; that, certainly. But it also seems to make Mark out an absolute idiot. Just suppose for a moment that, for urgent reasons which neither of you know anything about, he had wished to get rid of his brother. Would he have done it like that? Just killed him and then run away? Why, that’s practically suicide—suicide whilst of unsound mind. No. If you really wanted to remove an undesirable brother, you would do it a little bit more cleverly than that. You’d begin by treating him as a friend, so as to avoid suspicion, and when you did kill him at last, you would try to make it look like an accident, or suicide, or the work of some other man. Wouldn’t you?”
“You mean you’d give yourself a bit of a run for your money?”