In the Arabian Nights’ Entertainments is told the story of Ali Baba and the Forty Thieves. In this, at the mention of the magic word “Sesame,” the ponderous rocky portal of the treasure cave swung open or shut, according to its previous position.

And now, as Ned, Bob, and Jerry stood outside the cabin door, through which they had a glimpse of the well-remembered figure, and as together they uttered the magic word “Professor Snodgrass,” the same thing happened as happened to Ali Baba.

The door of the cabin was quickly shut, and not by the figure seated at the table before the mass of papers.

For a few seconds the three lads remained transfixed with surprise. They looked at one another, then glanced at the closed door, and then peered into each others’ faces.

[102]

Jerry was the first to recover the use of his voice.

“Did you see that, fellows?”

“Did we see it?” echoed Ned. “I should say so!”

“What does it all mean?” asked Bob. “Why should our old friend, Professor Snodgrass, treat us like that—shutting the door in our faces?”

“He didn’t!” declared Jerry.

“He did!” asserted Bob. “I saw him!”

“You saw the door close,” went on Jerry. “But the professor didn’t shut it. If you had been standing where I was, you could have observed that. There was some one else in the room who acted for him.”

“That’s right!” chimed in Ned. “He didn’t even see us. He didn’t look up once from his papers. It was the same old Professor Snodgrass—more intent on finding out how many legs some new kind of ant has than on his meals. Yes, the same old professor!”

“Are you sure about that?” asked Jerry.

“Sure of it?” reiterated Ned. “Why, of course! Aren’t you?”

“You called his name out, just as we did, and then the door went shut,” declared Bob. “You spoke his name.”

“Yes; and at the time I really thought it was the professor,” admitted Jerry. “But when I[103] think of what took place I begin to have my doubts.”

“Professor Snodgrass never acted that way before, that’s sure,” and Ned seemed siding with Jerry Hopkins. “Every other time he’s seen us he’s been tickled to death. This time——”

“He didn’t see us this time—that’s all there is to it,” declared Jerry. “Professor Snodgrass or not, whoever is in that room never looked up to see us, though he—whoever he is—may have heard us call out the name.”

“If it isn’t the professor who is it?” demanded Bob.

“Who’s the fellow I had the row with in the restaurant?” Jerry countered.

“Oh! Le cochon!” Bob exclaimed. “That’s so! He does look a lot like our friend. But not from the front, Jerry Hopkins! Not from the front!” he added quickly, as he recalled that circumstance, and the fact that this time they had had a full-face view of the man now sitting behind the closed cabin door. “The pepper-pot looks like the professor from the back view, but not from the front. We proved that several times.”

“And besides,” went on Ned, “this isn’t the mysterious cabin, either. There are no marines on guard here.”

“I grant you that,” said Jerry, and he was smiling at his two chums in a manner that, had they[104] not been so excited, would have roused their curiosity.

“And this isn’t the same cabin, either!” reiterated Ned. “The one where the marines are on guard, and where we think the pepper-pot is held a prisoner, is on the deck below.”

“Are you sure of that?” asked Jerry, and the manner of his asking made both Ned and Bob look more closely at the corridor in which they were then standing. Next they glanced at the closed door, noting the number, and with one accord they exclaimed:

“It’s the same!”

“That’s what I thought you’d say,” remarked Jerry, with a little nod of satisfaction. “But we might as well hike along. No use standing here talking over the mystery. Besides, the professor may not like it.”

“I thought you said it wasn’t the professor,” said Ned.

“No, I only said I had my doubts,” corrected Jerry. “I don’t really know what to think.”

“As you say, it’s a mystery,” conceded Bob. “But can’t we get to the bottom of it? Say, all sorts of things are happening on our homeward trip. Here we are delayed because of some mysterious explosion on board, there’s a mysterious prisoner in a mysterious cabin guarded by marines, and now we think we see in the same cabin the[105] real professor. S............