d screwed it fast.

The problem had to stand over, as he wished to complete his
investigation of the remainder of the building. But though he searched
the entire premises with the same meticulous thoroughness that he had
displayed in dealing with the papers, he came on nothing else which in
any way excited his interest.

He let himself out and, relocking the various doors behind him, walked
to Hassle and from there returned to his hotel in Hull.

He was a good deal intrigued by his discovery of the secret telephone.
That it was connected up and frequently used he was certain, both from
the elaboration of its construction and from the marking round the
cupboard keyhole. He wondered if he could without discovery tap the
wires and overhear the business discussed. Had the wires been carried
on poles the matter would have been simple, but as things were he would
have to make his connection under the loose board and carry his cable
out through the wall and along the shore to some point at which the
receiver would be hidden--by no means an easy matter.

But in default of something better he would have tried it, had not a
second discovery he made later on the same evening turned his thoughts
into an entirely new channel.

It was in thinking over the probable purpose of the telephone that he
got his idea. It seemed obvious that it was used for the secret side of
the enterprise, and if so, would it not most probably connect the import
depot of the secret commodity with that of its distribution?
Ferriby wharf was the place of import, but the distribution, as the
conversations overheard indicated, lay not in the hands of Benson but of
Archer. What if the telephone led to Archer?

There was another point. The difficulty of laying a secret land wire
would be so enormous that in the nature of things the line must be
short. It must either lead, Willis imagined, to the southern bank of the
estuary or to somewhere quite near.

But if both these conclusions were sound, it followed that Archer
himself must be found in the immediate neighborhood. Could he learn
anything from following up this idea?

He borrowed a directory of Hull and began looking up all the Archers
given in the alphabetical index. There were fifteen, and of these one
immediately attracted his attention. It read:

"Archer, Archibald Charles, The Elms, Ferriby."

He glanced at his watch. It was still but slightly after ten. Taking his
hat he walked to the police