The detective paused and glanced at his watch. “We must go,” he said, staring at Loris with soft interest. “I’m afraid we’re keeping you from your sleep.”
“No. I want to ask you another question,” she said eagerly. “I’m still in doubt about the slot booths at Grand Central. Why were they used?”
“As a throw off! That is what the English would call shunting. Electricians use the same word. It means diverting a current or a connection. Cuthbert did this so that his trail would be harder to check up. He thought of almost everything.”
“He missed his vocation!” interjected Nichols.
“And misused his talents,” added Loris. “Think of being clever enough to do all of those things, and stoop to murder. He paid ten times over. He must have been under that man Morphy’s power. So many men were. I heard father say that when Morphy was arrested. He said Morphy was the most dangerous man in the world. That he would cause trouble sooner or later.”
Drew rose and nodded. “He did that!” he exclaimed with conviction. “He came very close to getting away with it. But for the magpie and the fact that he ’phoned from the prison at the same time your father was murdered, there would have been no clew. Cuthbert would have entered this house after you were slain, and removed the receiver. That would have thrown the case into one of the unsolved mysteries. Electricity is a dangerous tool in the hands of clever crooks.”
“It leaves no trace!” said Delaney, rising and standing by his chief. “It isn’t made out of anything except little shakes in the wire or something like that.”
Drew smiled good-naturedly. “It’s a mystery to most people,” he said, turning toward the windows and listening. “It’s a bigger mystery to a woman than to a man,” he added. “It’s a good agent if properly used and kept within bounds. It brings back life as well as takes it. It creates and also destroys. No one knows what it is. All that we do know about it is its action on material substances—the power to transform mechanical energy into vibrations and then back again into mechanical energy.”
“Like a voice on a wire?” asked Loris.
“Yes, Miss Stockbridge. The mechanical vibration of a diaphragm in a telephone transmitter is changed to electrical vibrations, passes along a wire and changes back to the same thing we had at the beginning. Cuthbert took advantage of this fact. All that was sent into the library was Morphy’s voice on the wire. The wire left no trace. The voice actuated the diaphragm and at the same time the fine heating coil at the cap on the cartridge. The energy of the voice was sufficient to raise the temperature of the coil. This raise in temperature flashed some compound set in the wire. The flash started the fulminate of mercury in the cap. The cap exploded the smokeless powder. It was a series of steps each a little higher than the one below it.”