Harry had learned all that he desired to know.
The enemy had not yet arrived; at least he had not invaded the professor’s study. The next task was to search the house.
He went back to find Arlette.
To his surprise, the girl was not in the kitchen. Why had she left her post? Had she decided to search the house? That was not in the arrangement.
Arlette would have remained here as she promised. There was only one possible explanation of her disappearance. She had been surprised and captured!
The enemy could not have come from the outside, nor from upstairs; Arlette had commanded both the door, and the steps which led to the second floor.
She must have been seized by some one lurking in the kitchen.
Harry thought of the stairs that led to the basement. He turned on his flashlight, and saw that the cellar door was open. It was a heavy door, and had usually been shut and locked.
The gleam of his light revealed a small object on the floor. It was Arlette’s hat. Her captor had carried her to the cellar.
It required only a few minutes for Harry to investigate the cellar. There were several rooms; but all the doors were open. His flashlight showed him the chemical laboratory, a workroom, and a storeroom; then he came upon an archway.