“Very convenient having these museum lights on all night,” Sir Clinton remarked. “We don’t need to muddle about with the flash-lamp. Now just wait here for a moment, and don’t speak a word. I’m going upstairs.”
He ascended to the first floor, entered Foss’s room and picked up the otophone, with which he returned to his companions.
“Now we can get to work,” he whispered, leading the way into the museum. “Just lock that door behind us, Inspector.”
Followed by the other two he stepped across the museum to the bay containing the safe. There he put the otophone on the floor and opened the case of the instrument. From one compartment he took an ear-phone with its head-band. A moment’s search revealed the position of the connection, and he plugged the ear-phone wire into place in sockets let into the outside of the attaché case. A little further examination revealed a stud beside the leather handle, and this Sir Clinton pressed.
“That should start the thing,” he commented.
He lifted the hinged metal plate slightly and peered into the cavity which contained the valves.
“That seems all right,” he said, as his eye caught the faint glow of the dull emitters.
Shutting down the plate again, the Chief Constable put his finger into the compartment from which he had taken the ear-phone, pressed a concealed spring, and pulled up the floor of the compartment.
“This is the microphone,” he explained, drawing out a thick ebonite disk mounted on the false bottom of the compartment. “It’s attached to a longish wire so that you can take it out and put it on a table while the case with the valves and batteries lies on the floor out of the way. Now we’ll tune up.”
He brought microphone and ear-phone together, when a faint musical note made itself heard. Then he handed the microphone to Cecil.