"It's almost the same thing. Both answers will come with hard work and plenty of it. We must keep along the main stem. Truth is a tree with many branches. It rises from the roots named cause, and reaches the top called effect. It springs from motive up to crime in one straight stem. We must trim away the branches and the false-work, and then we can see the trunk." "There's one I'd like to trim right now," said Delaney, pausing in his snow-caked stride. "Which one?" asked Drew. "That noise in the library like a cat getting its tail twisted." "I can explain that!" "It's been driving me to drink, Chief." "The telephone company, Delaney, have a device they call a howler. They cut this device in on the wire when a receiver is left off the hook. It is simply a high-frequency current generated for the purpose of vibrating the receiver's diaphragm until somebody hears the noise and puts the receiver back on the hook." "It's a howler, all right, Chief!" "Oftentimes a book or magazine gets under a receiver and lifts it up an inch or more. This attracts the attention of the central operator who thinks somebody is trying to get a number. When the situation is clear to her that the receiver is off the hook, or that the circuit is closed without anybody being at the receiver end, she notifies the wire-captain or chief-operator. It was either one or the other who put the howler on after Stockbridge was shot and the 'phone had fallen to the floor. Is that satisfactory? Does that explain the noise we heard in the library before we broke down the door?" "I see now, Chief. I thought all along it was spirits like the rest of the job. Outside of spirits, what is the answer to the things that happened in that house? I know it. I deduct it, Chief. The old man was expecting somebody all of the time. He let this somebody into the library when the butler wasn't looking. Maybe it was a woman, for all we know. Maybe a German spy. Maybe anybody. This somebody got in an argument with him over spoils on some deal, and shot him dead. That's my idea, Chief!" "You've missed your profession, Delaney. You've disgraced the firm! How did the library door get locked on the inside? How did that happen? Did Stockbridge, shot through the brain, rise and do it? It was mighty well locked--you remember!" "I never thought of that," admitted the operative. "Then it looks, Chief, as if it was a case of suicide." "Fosdick said the same thing without having many facts. How could a right-handed man shoot himself behind the left ear? How could he do a thing like that and then get rid of the weapon without leaving a trace of it? How--oh, well, get facts and you won't ask such questions!" "Then it was done by an outsider?" blurted Delaney, staring through the wind-blown snow which came off the housetops. "It was done by the fellow who 'phoned and wrote that letter, or had the letter written? I don't see how he could do it!"