Gilbert nodded his agreement. He had listened carefully to his father, but at the same time had been trying to understand how the mechanism was worked by which the chamber was opened and closed. It baffled him, however, and he desisted from the attempt. "What do you make of it?" asked the father. "Do you believe Whittaker right in thinking the chamber was opened last night?" inquired Gilbert. "I do." "But that he was wrong in putting it down to a burglar?" "Yes. Do burglars break into lawyer's rooms? I don't mean to say that such a thing is impossible, for valuable documents have been stolen--you can imagine that." "Of course. But if the secret chamber was not opened by a burglar, then by whom was it opened?" "That is the question," said Eversleigh, gazing earnestly at his son. "Whoever opened the secret chamber knew of its existence," Gilbert went on, thinking the matter out aloud. "Undoubtedly. He knew of its existence, and he also had the means of opening it." Gilbert suddenly started, for an extraordinary notion had come into his mind. His father saw the start, and thought he knew its meaning. The two men looked at each other strangely. "Only two men in the world, I feel certain, knew of that chamber," Eversleigh resumed. "One was the mechanic who devised and made it, the other was----" "Cooper Silwood!" exclaimed Gilbert. "Yes, Cooper Silwood." "But Silwood is dead, so you would say that it was the other? That seems absurd." "It is absurd. What would the mechanic who made the box care about taking anything out of the secret chamber? Once his job of making the thing was finished, he would be finished with it altogether. No, it was not the mechanic." Gilbert was silent. "Don't you see?" asked Eversleigh. "Silwood!" "Precisely." "But that is impossible. Dead men do not open secret chambers," said Gilbert, but there was something curious and suggestive in the manner of his saying it. "No. Dead men do not open secret chambers, but living ones do. Silwood is not dead! He is alive!" Eversleigh's voice rose into a shout and then cracked. "It seems inconceivable." "Yet there is no other conclusion. The maker of the box being out of the question, it follows that it must have been Silwood. I believe he was here last night and removed from the secret chamber something of particular value to him." "Silwood might have told some one of it," objected Gilbert. "Is it likely? You know he was the least communicative of men." "What about Williamson?" "I feel confident he knew nothing of it either. Don't you see this secret chamber was a receptacle in which Silwood hid papers or other things he had an object in concealing? You may be certain he told no one of it. If he had told any one, would he not have told me? No, Gilbert; from the moment I knew of Whittaker's discovery I suspected the truth." "But the certificate of his death?" "It was a false certificate."