When several months had elapsed, the Pinkertons were called into the case. They began by carefully studying certain communications that had been received by the bank directors from persons claiming to have in their possession the missing securities. The first of these communications was dated New York, February 27, 1876, about a month after the robbery. It ran as follows, the letters of each word being carefully printed with a pen, so that there was little chance of identification through the handwriting:
"Dear Sirs: When you are satisfied with detective skill you can make a proposition to us, the holders, and if you are liberal we may be able to do business with you. If you entertain any such ideas, please insert a personal in the New York 'Herald.' Address to XXX, and sign 'Rufus,' to which due attention will be paid. To satisfy you that we hold papers, we send you a couple of pieces."
[No signature.]
No attention had been paid to this letter, although two certificates of stock accompanied it which had undoubtedly been in the bank's vault. Three other letters of a similar nature had been received later. To one of these the bank people had sent a guarded reply, which had called forth the following response, dated New York, October 20, 1876:
"Gentlemen: Since you have seen fit to recognize the receipt of our letter, we will now send you our price for the return of the goods. The United States coupon bonds and money taken cannot be returned; but everything else—bonds, letters, and papers, to the smallest document—will be returned for one hundred and fifty thousand dollars. If these figures suit you, we will make arrangements, according to our promise, and you may have the goods as soon as preliminaries can be arranged for the safe conduct of the business. If you agree to this price, insert in the New York 'Herald' personal column the simple word 'Agatha.'
"Respectfully, etc.,
"Rufus."
The special value of these letters was in helping the detectives to decide which one of several gangs of bank robbers then operating in the country was most likely to have committed the crime. Being familiar with the methods of each gang, Robert Pinkerton was able to draw useful inferences from evidence that would otherwise have been insignificant. He knew, for instance, that the notorious gang headed by James Dunlap would be more apt than any other to thus negotiate for the return of all the securities in a lump, since it was Dunlap's invariable rule to insist upon personally controlling the proceeds of his robberies until final disposition was made of them. On the other hand, the gangs headed respectively by the notorious "Jimmy" Hope, "Worcester Sam," and George Bliss might have divided the securities among the members, and then tried to negotiate a compromise on the individual portions.
A fact of much significance to the Pinkertons was the rather remarkable interest in the case, and apparent familiarity with it, shown by one J. G. Evans, an expert in safes and vaults and the representative of one of the largest safe-manufactories in the country.
The day after the robbery Evans had been at Bristol, Connecticut, in the interest of his firm, who, on receipt of the news, had immediately wired him to proceed to Northampton. His presence in Northampton was regarded as nothing strange, for he had been there several times during the months just preceding the robbery, and once had inspected the lock and dials of the vault of the robbed bank. What did seem a little strange, however, was Evans's evident interest in the negotiations for a compromise. On a dozen different occasions he talked with the president and other officers of the bank regarding the robbery, and insinuated quite plainly that he might be in a position to assist them in recovering their lost securities. A few months after the robbery he even went so far as to tell one of the directors that he could name the members of the gang.