“The electric switch on Darcy’s table,” was the answer.  “I couldn’t help hearing what you said, Mr. Kettridge,” said Carroll, “and I don’t know as I would have tried not to if I could.  This is important.  I rather guess it makes it look a bit bad for your friend, Colonel Ashley,” and there was a sneer in the words.

“Well, I don’t know,” was the cool response.  “The wires, as I understand it, are to run an electric lathe, and they might easily have become crossed.”

“Oh, yes, of course!” admitted Carroll.  “And then, again, they might have been crossed on purpose.  It’s a new stunt—­electrically shocking an old lady before you bang her over the head or stab her, but it’s a good one.  I’ll have a look at that switch.  I thought maybe I might find something interesting here when I heard about the shock to the old servant, and I didn’t miss my guess.”

There was nothing for the colonel or Mr. Kettridge to say or do, and they remained passive while Carroll took his time looking about.  Then he telephoned for Haliday of the prosecutor’s office, and also for the chief electrician of the police signal system, and all three spent some time looking at the wires and testing them.

“What do you think about it?” asked Mr. Kettridge of the colonel, when the store was again dim and quiet.

“What do I think?  I don’t know!  I’m going to have a talk with Darcy in the morning, and if I find he’s been deceiving me—­ Well, I’ll drop his case, that’s all.”

If Darcy simulated surprise when, the next morning at the jail, told by the colonel of what had happened to Sallie Page, the prisoner was a consummate actor, the detective thought.

“Colonel Ashley!” Darcy exclaimed.  “I never knew that my lathe wires crossed or connected with any circuit that might shock a person.  It is true I had the wires run in secretly, as I didn’t want my cousin to know about them.  She didn’t favor my experiments on the electrical lathe, and I had to keep quiet about it.

“But I never strung those wires to shock her, and of course you can easily imagine I never could plan to injure Sallie Page that way, or the young lady who was knocked down the other day.”

“Well, Darcy, you may be telling the truth, and, again, you may not,” and the colonel’s voice was as noncommittal as possible.  “But I am bound to point out to you that the prosecution will make the most of this, and that—­it looks bad for you.”

“I know it does, Colonel.  But I had no more to do with my cousin’s death than Carroll or you.  Nor have I the least suspicion who did kill her.  My God! what object would I have?” and he turned and paced up and down.

“Well I’ll do the best I can,” said the colonel.  “But I must say it looks black.  Then you never knew your wires might, by the closing of the switch on your table, shock some one standing near the show case?”

“I never dreamed of it!  The wires must have been changed since I used them.”