Also a personal one. He had every reason to believe that he would never be discovered."

"Then, Mr. Drew, he would have called me up on the phone later and done what he did--to father? He would have told me who he was over the telephone, and--and----"

"Yes, Miss Stockbridge. Yes, be calm, though. He is beyond the pale now. You will never hear from him again. Be a.s.sured of that!"

Drew leaned in his chair and glanced at Delaney. The big operative fidgeted in his seat, squirmed, reached for the tea-pot, then drew back his hand and started drumming the table with his fingers.

Nichols disengaged his arm from behind Loris and squared his shoulders.

He moved forward. "I'm going to ask a question for Miss Stockbridge,"

he said. "Did you ever suspect her?"

"Never!" declared Drew.

"Or me?"

The detective hesitated before he answered. His smile cleared the air as he said. "Once--for about an hour. That was when I found out that you were partly German. I got over it, though."

"So did I," declared Nichols. "I got over the German part in no time. I enlisted!"

"That's a good answer! The best one I know!"

Delaney turned to his chief. He drew in his legs. "There's a question I'd like to ask," he said.

"What is it?"

"That magpie?"

Drew eyed Loris. "It's her bird now," he said. "She may not want it dragged back here again. I shouldn't think she would."

"I don't!" exclaimed Loris. "I wish that you would explain how you followed the clew, though. It talks so seldom, and then when it does talk it says such nonsense it's a perfect enigma."

"That bird," said Drew, "was the fine turning point of the case. Before it was brought into the office, downtown, I had no clew to start from.

There was no indication to show from whence the blow had fallen. Your father was slain for a motive. He was talking to Morphy when he died.

Cuthbert had connected the two men."

"Through the two booths?" asked Loris.

"Yes. Through the booths at Grand Central. Their conversation was probably a brief one. Morphy undoubtedly gloated a minute or two, then told Mr. Stockbridge that his time had come on this earth. Naturally Mr. Stockbridge asked who was talking. Morphy answered by stating who he was, and also that he was at Sing Sing. Mr. Stockbridge repeated this statement aloud. He probably said, 'What, Sing Sing?' or 'Ah, Ossining!' or words to that effect. The bird heard it and remembered it."

"How strange!" exclaimed Nichols.

"Not at all," said Drew, leaning forward. "It was just like a magpie to pick out the one salient part of a conversation and repeat it. The couplet 'Sing Sing' was one it had never heard. It is so striking to even a bird. It probably came with such emphasis, there was no forgetting it!"

The group facing the detective was silent for a long minute. Delaney moved uneasily as Nichols toyed with his cup. Loris breathed in suppressed wonder at the tiny clew which had overthrown the best laid plans on the part of Morphy and his confederate. It was like an echo of a dead voice coming back to confront a murderer. She shivered as she widened her eyes and stared at Drew.

"There's another question," she said. "How did the trouble-man get into this house in the first place, Mr. Drew?"

"I was responsible. He forced my hand!"

"How?"

"By a clever subterfuge. He disconnected the library telephone wires at the junction-box in the alley. He knew that sooner or later Mr.

Stockbridge would try to use the 'phone. He couldn't get a connection, or I couldn't. It was the time I tried to 'phone and then notified Gramercy Hill Exchange through another 'phone. He was listening in and consequently caught the gist of my orders to Harrigan. He hurried to Gramercy Hill Exchange and there met Frisby, another trouble-man, starting out to investigate my complaint. He took Frisby's place, hurried over and closed the library connection and then came into the house, stating that we had sent for him."

"Clever," said Nichols. "That was clever, wasn't it?"

"Remarkably so!" exclaimed Drew. "It was a case of making the detective on the premises act as a tool. It was like a safeblower asking a night watchman to move a safe out on a truck. I never suspected that fellow at all. I hardly looked at him when he was testing the connections in the library. I even heard him rattling a pair of pliers over the binding posts on the receiver. That was the time he took the old one off and put on the loaded pistol. It was done very quickly."

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, pa.s.ses 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."

"Was there any other way of doing the same thing?" Nichols inquired, as he rose lankily and stood over Loris.

"Yes!" declared Drew. "I can look back over what I found in the technical books about electricity and telephony and see several other ways for Cuthbert to accomplish the same result. The electrical pistol did not necessarily have to be actuated by the human voice."

"How terrible!" Loris whispered, with her brow puckering. "Perhaps others will use the same idea to slay their enemies."

"We'll keep it a close secret," the detective said. "It rests with us four, now. Outside of us, there is only Morphy who knows."

"How else could the pistol be discharged?"

"Two other ways that I see, Miss Stockbridge. It would be rather easy to arrange a little magnetic trigger in the receiver. This trigger could be actuated by an excess of current--say the connecting of a hundred and ten volt lighting circuit on the line. It might burn out the magnet wiring, but it would also release the trigger and fire the cartridge."

"That's like a door-catch?"

"Yes," said Drew. "Like a door-catch operated by a magnet or like the firing pin of a large cannon. They're not all operated by lanyards.

Some work with push-b.u.t.tons."