“Of course,” said Lexman, leaning back and toying with a salt-spoon, “in writing a story where one hasn't got to deal with the absolute possibilities, one could always have made Kara have a safe of that character in order to make his escape in the event of danger. He might keep a rope ladder stored inside, open the back door, throw out his ladder to a friend and by some trick arrangement could detach the ladder and allow the door to swing to again.” “A very ingenious idea,” said T. X., “but unfortunately it doesn't work in this case. I have seen the makers of the safe and there is nothing very eccentric about it except the fact that it is mounted as it is. Can you offer another suggestion?” John Lexman thought again. “I will not suggest trap doors, or secret panels or anything so banal,” he said, “nor mysterious springs in the wall which, when touched, reveal secret staircases.” He smiled slightly. “In my early days, I must confess, I was rather keen upon that sort of thing, but age has brought experience and I have discovered the impossibility of bringing an architect to one's way of thinking even in so commonplace a matter as the position of a scullery. It would be much more difficult to induce him to construct a house with double walls and secret chambers.” T. X. waited patiently. “There is a possibility, of course,” said Lexman slowly, “that the steel latch may have been raised by somebody outside by some ingenious magnetic arrangement and lowered in a similar manner.” “I have thought about it,” said T. X. triumphantly, “and I have made the most elaborate tests only this morning. It is quite impossible to raise the steel latch because once it is dropped it cannot be raised again except by means of the knob, the pulling of which releases the catch which holds the bar securely in its place. Try another one, John.” John Lexman threw back his head in a noiseless laugh. “Why I should be helping you to discover the murderer of Kara is beyond my understanding,” he said, “but I will give you another theory, at the same time warning you that I may be putting you off the track. For God knows I have more reason to murder Kara than any man in the world.” He thought a while. “The chimney was of course impossible?” “There was a big fire burning in the grate,” explained T. X.; “so big indeed that the room was stifling.” John Lexman nodded. “That was Kara's way,” he said; “as a matter of fact I know the suggestion about magnetism in the steel bar was impossible, because I was friendly with Kara when he had that bar put in and pretty well know the mechanism, although I had forgotten it for the moment. What is your own theory, by the way?” T. X. pursed his lips.