He glanced through the high windows at the other end of the room.  She laid her fingers upon his arm and led him towards the door.

“Quietly, please,” she whispered.  “Try and imagine that you are in a house of conspirators.”

She led him up the quaint stone staircase, spiral-shaped, to the first floor.  Arrived there, she paused to listen for a moment, then breathed a little more freely and led him to a small sitting-room at the end of a long passage.  It was a pleasant little apartment and looked sheer out over the sea.  She threw herself down upon a sofa with a sigh of relief, and pointed to a chair.

“Do sit down, Captain Granet,” she begged.  “I am really not in the least insane but father is.  You know, I got back on Wednesday night and was met at once with stern orders that no visitors of any sort were to be received, that the tradespeople were to be interviewed at the front gates—­in fact that the house was to be in a state of siege.”

Granet appeared puzzled.

“But why?”

“Simply because dad has gone out of his senses,” she replied wearily.  “Look here.”

She led him cautiously to the window and pointed downwards.  About fifty yards out at sea was a queer wooden structure, set up on strong supports.  From where they were, nothing was to be seen but a windowless wall of framework and a rope ladder.  Underneath, a boat was tethered to one of the supports.  About thirty yards away, a man was rowing leisurely around in another small boat.

“That’s where father spends about twelve hours a day,” she said.  “What he is doing no one knows.  He won’t even allow me to speak of it.  When we meet at meals, I am not supposed to allude to the fact that he has been out in that crazy place.  If ever he happens to speak of it, he calls it his workshop.”

“But he is not alone there?” Granet asked.

“Oh, no!  There are two or three men from London, and an American, working with him.  Then do you see the corner of the garden there?”

She pointed to a long barn or boathouse almost upon the beach.  Before the door two sentries were standing.  Even from where they sat they could hear the faint whirr of a dynamo.

“There are twenty men at work in there,” she said.  “They all sleep in the barn or the potting sheds.  They are not allowed even to go down to the village.  Now, perhaps, you can begin to understand, Captain Granet, what it is like to be here.”

“Well, it all sounds very interesting,” he remarked, “but I should think it must be deadly for you.  Your father invents no end of wonderful things, doesn’t he?”

“If he does, he never speaks about it,” the girl answered a little bitterly.  “All that he wants from me is my absence or my silence.  When I came back the other night, he was furious.  If he’d thought about it, I’m sure he’d have had me stay in London.  Now that I am here, though, I am simply a prisoner.”