"I shall be delighted," said T. B.
He was curious to learn anything that the house or its custodian could teach him. Dr. Fall's room was on the first floor, immediately over the entrance hall, a plain office with a door leading to a cosily, though comparatively expensively furnished bedroom. By the side of the doctor's bed was a round pillar, which looked for all the world like one of those conventional and useless articles of furniture which the suburban housewife employs to balance a palm upon.
"Look down into that," said the doctor.
T. B. obeyed. It was quite hollow, and a little way down was what appeared to be a square sheet of silver paper. It was unlike any other silver paper because it appeared to be alive. He could see figures standing against it, two figures that he had no difficulty in recognizing as Ela and Johnson.
"It is a preparation of my own," said the doctor. "I thought of taking out a patent for it. An adjustment of mirrors throws the image upon a luminous screen which is so sensitive to light that it can record an impression of your two friends even in the semi-darkness of the hall."
"Thank you," said T. B.
There was nothing to do but to accept his defeat as graciously as possible. For baffled he was, caught at every turn, and puzzled, moreover, by his extraordinary experience.
"You will find some difficulty in opening the door," said the pleasant Doctor Fall.
"In that I think you are mistaken," smiled T. B.
The doctor stopped to switch on the light, and the two discomforted detectives watched the scene curiously.