Hunt applied himself once again to a study of the blocks, and then he made a third discovery, which, though he could not at first see its drift, struck him nevertheless as being of importance. He found that the faked block was always one of a pair. Within a few pages either in front of or behind it was another block containing particulars of a similar consignment, identical, in fact, except that the brandy item was missing.
Hunt was puzzled. That he was on the track of the fraud he could not but believe, but he could form no idea as to how it was worked. If he were right so far, the blocks had been made out in facsimile in the first instance, and later the brandy item had been added to one of each pair. Why? He could not guess.
He continued his examination, and soon another interesting fact became apparent. Though consignments left the works at all hours of the day, those referred to by the first one of each between the hours of four and five. Further, the number of minutes past one and past four were always identical on each pair. That showed the brandy item was nearly always the later of the two, but occasionally the stuff had gone with the one o’clock trip.
Hunt sat in the small office, of which he had been given undisturbed possession, pondering over his problem and trying to marshal the facts that he had learned in such a way as to extract their inner meaning. As far as he could follow them they seemed to show that three times each day driver Charles Fox took a lorry of various liquors into Hull. The first trip was irregular, that is, he left at anything between seven-thirty and ten-thirty a.m., and his objective extended over the entire city. The remaining two trips were regular. Of these the first always left between one and two and the second the same number of minutes past four; both were invariably to the same one of the five large tied houses already mentioned; the load of each was always identical except that one—generally the second—had some kegs of brandy additional, and, lastly, the note of this extra brandy appeared always to have been added to the certificate after the latter had been made out.
Hunt could make nothing of it. In the evening he described his discoveries to Willis, and the two men discussed the affair exhaustively, though still without result.
That night Hunt could not sleep. He lay tossing from side to side and racking his brains to find a solution. He felt subconsciously that it was within his reach, and yet he could not grasp it.
It was not far from dawn when a sudden idea flashed into his mind, and he lay thrilled with excitement as he wondered if at last he held the clue to the mystery. He went over the details in his mind, and the more he thought over his theory the more likely it seemed to grow.
But how was he to test it? Daylight had come before he saw his way; but at last he was satisfied, and at breakfast he told Willis his idea and asked his help to carry out his plan.
“You’re not a photographer, by any chance?” he asked.
“I’m not A1, but I dabble a bit at it.”