Though I had spoken in low tones, my own intense emotion made my words emphatic, and as I finished I was perhaps the more excited of the two.

For Hall’s composure had returned; his face resumed its natural color; his eyes their normal expression—­that of cold indifference.

“Mr. Burroughs,” he said quietly, “you must be insane.”

“That is no answer to my accusations,” I stormed.  “I tell you of the most conclusive evidence against yourself, and instead of any attempt to refute it you mildly remark, `you are insane.’  It is you who are insane, Mr. Hall, if you think you can escape arrest and trial for the murder of Joseph Crawford.”

“Oh, I think I can,” was his only answer, with that maddening little smile of his.

“Then where were you on Tuesday night?”

“Excuse me?”

“Where were you on Tuesday night?”

“That I refuse to tell—­as I have refused before, and shall always refuse.”

“Because you were here, and because you have too much wisdom to try to prove a false alibi.”

He looked at me half admiringly.  “You are right in that,” he said.  “It is extremely foolish for any one to fake an alibi, and I certainly never should try to do so.”

“That’s how I know you were here,” I replied triumphantly.

“You do, do you?  Well, Mr. Burroughs, I don’t pretend to misunderstand you—­for Miss Lloyd has told me all about Mrs. Cunningham and her bag that she left in the train.  But I will say this if you think I came out on that midnight train, go and ask the conductor.  He knows me, and as I often do come out on that train, he may remember that I was not on it that night.  And while you’re about it, and since you consider that late newspaper a clue, also ask him who was on the train that might have come here afterward.”

If this was bluffing, it was a very clever bluff, and magnificently carried out.  Probably his hope was that the conductor could not say definitely as to Hall’s presence on the late train, and any other names he might mention would only complicate matters.

But before I left I made one more attempt to get at this man’s secret.

“Mr. Hall,” I began, “I am not unfriendly.  In fact, for Miss Lloyd’s sake as well as your own, I should like to remove every shadow of suspicion that hovers near either or both of you.”

“I know that,” he said quickly.  “Don’t think I can’t see through your `friendliness’ to Miss Lloyd!  But be careful there, Mr. Burroughs.  A man does not allow too many `friendly’ glances toward the girl he is engaged to.”

So he had discovered my secret!  Well, perhaps it was a good thing.  Now I could fight for Florence more openly if necessary.

“You are right, Mr. Hall,” I went on.  “I hold Miss Lloyd in very high esteem, and I assure you, as man to man, that so long as you and she are betrothed, neither of you will have cause to look on me as other than a detective earnest in his work in your behalf.”