Concealed in a woollen sack, with the slender shaft thrust through and through the folds, was a peculiarly long, stout, and sharp hat pin.  Rawlins drew it out.  He held it up triumphantly.

“Now maybe we’re not getting somewheres!  That’s the boy that did the trick in both cases, and it’s what scratched Mr. Paredes.  Maybe you noticed how quickly she came upstairs to hide this when she got in.”

“Good work, Rawlins,” Robinson said.

He glanced at Bobby and Graham.

“Have either of you seen this deadly thing before?”

Bobby wouldn’t answer, but after a moment’s hesitation Graham spoke: 

“There’s no point in lying, Bobby.  Katherine knows nothing of this.  I disagree with Rawlins.  If she had been working with Paredes, which is unthinkable, she’d never have made such a mistake.  She wouldn’t have struck him.  I have seen her wear such a pin.”

“If she didn’t cut him with it,” Rawlins reasoned, “who else could have got it out of here and put it back to-night when she kept her door locked?”

“There’s no getting around it,” Robinson said.  “Take charge of these things, Rawlins.  Put them in a safe place.”

“What are you going to do?” Bobby asked.

“I’m afraid there’s only one thing to do,” Robinson answered.  “I’ll have to arrest you both.  One of you used this pin in the old room.  It doesn’t make much difference which one.  You’ve been working together, and we’ll find out about Paredes later.”

“You’re making a terrible mistake,” Bobby muttered.  “You don’t know Katherine or you couldn’t suspect her of any share in such crimes.  Give me until morning to prove how wrong you are.”

“What would be the use?” Robinson asked.

“If you’ll do that, I will get the truth for you—­the whole truth, how the room was entered, everything.  I swear it, Robinson.  Only a few hours.  Let me carry out my plan.  Let me offer myself to the dangers of the old room as Howells and my grandfather did.  Your case is no good unless you can explain the miracle to-night.  Give us this chance.  Then in the morning, if nothing happens and you still think I’m guilty, lock me up, but for God’s sake, Robinson, leave her out of it.”

Graham walked to the window and flung it open.  A violent gust of wind swept in, carrying a multitude of icy flakes.

“The storm is worse,” he said.  “No one is likely to try to escape from this house to-night.”

Bobby stretched out his hand.

“You can’t expose her to that.”

Rawlins hadn’t forgotten the sense of fellowship sprung from the pursuit of Paredes through the forest.

“He’s right, Mr. Robinson.  You could lock up a dozen people.  You might send them to the chair without uncovering the real mystery of the Cedars.  Maybe he might find something, and he’d be as safe in that room as in any jail I know of.  I mean one of us would be in the library and the other in the corridor outside the broken door.  How could he reasonably get out?  If there was an attempt to repeat the trick we’d be ready.  As for the girl, it’s simple enough to safeguard against her getting away before morning.  As Mr. Graham says, no one’s likely to run far in this storm, anyway.”