The Seed of Empire by Fred M. White

A sudden change seemed to have come over Venables. He was no longer the light-hearted, easy-going war correspondent, cheerfully taking his life in his hands and devoted to the interests of his paper, but a keen and eager individual with important work in hand.

"One of you stand in the doorway," he said, "and try and look as if you are just hanging about there till the woman comes back. This is the thing that I have been looking for for a long time. I suppose I have located at least a half a dozen of these during the last week, but I knew that there was one that had evaded me, and behold, here it is. You can see for yourselves how cleverly it has been arranged. The wire comes up under the floor boards, and you will notice how cunningly the instrument has been concealed in the false bottom of this old oak cradle. The other receiver, unless I am greatly mistaken, is in a wood not far behind the place where your trenches were. And from there again it will go underground back to one of the German batteries. Now what we have to do is to locate that German battery."