We could scarcely hear even now the faint throbbing of its engines.

Perhaps they had stopped and the boat was only gliding forward under their previous impulse.
It seemed, then, that this was indeed the submarine which Wells had watched, and it was returning to pass this night, like the last, within the shelter of the creek.
Why had it left the anchorage, if only to return?
Had it suffered some new disaster, which again impaired its power?
Or had it been before compelled to leave, with its repairs still unfinished?
What cause constrained it to return here?
Was there some imperious reason why it could no longer be turned into an automobile, and go darting away across the roads of Ohio?
To all these questions which came crowding upon me, I could give no answer.

Furthermore both Wells and I kept reasoning under the assumption that this was really the "Terror" commanded by the "Master of the World" who had dated from it his letter of defiance to the government.

Yet this premise was still unproven, no matter how confident we might feel of it.
Whatever boat this was, that stole so softly through the night, it continued to approach us.

Assuredly its captain must know perfectly the channels and shores of Black Rock Creek, since he ventured here in such darkness.