Gilbert broke off suddenly with a sharp ejaculation.
"You have thought of something, Mr. Gilbert?" suggested the inspector, giving him a keen look of inquiry.
"Yes, I have, and a very important thing it may prove too. It has been completely driven out of my mind by the dreadful discovery in Stone Buildings. Now I remember it, and I believe it may give us the key to the mystery."
"What is it?" asked Gale, as Gilbert paused, his face aglow with excitement.
"Before I went out to bring the interpreter something happened," said Gilbert. "Strange that I should have forgotten it so utterly! While my father and I were talking about Mr. Silwood's death, we were interrupted by a man, who had come in answer to the advertisement in the hope of getting the reward of a thousand pounds. The man was as hopeless-looking a waster and vagabond as any I ever saw, but he spoke like a man of education. And he told us that late on the night of the disappearance of Morris Thornton he was in Chancery Lane, and saw a workman coming out of the iron gate at the north-east corner of Lincoln's Inn."
"That is just where Mr. Silwood's chambers are, are they not?" asked Gale.
"Precisely; his rooms are on the top floor of the house at that very corner. Well, this workman behaved in a suspicious manner, and then disappeared. But he returned in about half an hour, and let himself into the Inn again by the iron gate."
"Wait a minute," said Gale. "You said a workman. What was a workman doing in the Inn at that time of night? And with a key which unlocked that gate?"
"These are puzzles, are they not?"
"You have certainly given me something to think over. Have you anything more to tell me about this workman?"