“Humph,” grunted Kennedy, as we were leaving the store.  “You wouldn’t believe it, but it is the hardest thing in the world to get an accurate description of any one.  The psychologists have said enough about it, but you don’t realise it until you are up against it.  Why, that might have been the DeMott woman just as well as the former Miss Sanderson, and the man might have been Bolton Brown as well as Dawson, for all we know.  They’ve both disappeared now.  I wish we could get some word about that photograph.  That would settle it.”

In the last mail that night Kennedy received back the letter which he had addressed to Michael Dawson.  On it was stamped “Returned to sender.  Owner not found.”

Kennedy turned the letter over slowly and looked at the back of it carefully.

“On the contrary,” he remarked, half to himself, “the owner was found.  Only he returned the letter back to the postman after he had opened it and found that it was just a note of no importance which I scribbled just to see if he was keeping in touch with things from his hiding-place, wherever it is.”

“How do you know he opened it?” I asked.

“Do you see those blots on the back?  I had several of these envelopes prepared ready for use when I needed them.  I had some tannin placed on the flap and then covered thickly with gum.  On the envelope itself was some iron sulphate under more gum.  I carefully sealed the letter, using very little moisture.  The gum then separated the two prepared parts.  Now if that letter were steamed open the tannin and the sulphate would come together, run, and leave a smudge.  You see the blots?  The inference is obvious.”

Clearly, then, our chase was getting warmer.  Dawson had been in Atlantic City at least within a few days.  The fruit company steamer to South America on which Carroll believed he was booked to sail under an assumed name and with an assumed face was to sail the following noon.  And still we had no word from Chicago as to the destination of the photograph, or the identity of the man in the Van Dyke beard who had been so particular to disarm suspicion in the purchase of the plate from the photographer a few days before.

The mail also contained a message from Williams of the Surety Company with the interesting information that Bolton Brown’s attorney had refused to say where his client had gone since he had been released on bail, but that he would be produced when wanted.  Adele DeMott had not been seen for several days in Chicago and the police there were of the opinion that she had gone to New York, where it would be pretty easy for her to pass unnoticed.  These facts further complicated the case and made the finding of the photograph even more imperative.

If we were going to do anything it must be done quickly.  There was no time to lose.  The last of the fast trains for the day had left and the photograph, even though it were found, could not possibly reach us in time to be of use before the steamer sailed from Brooklyn.  It was an emergency such as Kennedy had never yet faced, apparently physically insuperable.