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.
"My theory isn't very clearly formed," he said cautiously, "but so far as it goes, it is that Kara was lying on the bed probably reading one of the books which were found by the bedside when his assailant suddenly came upon him.