A CLUE

"That looks bad, don't it Frank?" Andy went on to remark, as he first glanced at the bogus collection of rare specimens, and then eyed his cousin humorously.

"One thing is sure, no man would go to the trouble and expense of buying even a dollar case of common butterflies unless he had some deep object in view, and you know that, Andy. This so-called professor must be a fraud, even if he doesn't turn out to be the man we think he is. Perhaps, he wanting to find out whether Hoskins had discovered that wonderful gold mine. Well, you needn't grin about it because stranger things have happened, I guess, now."

Andy ceased laughing and turned to look around the room.

"I wonder—" he began, and then stopped short.

"Now I can finish your sentence for you," said Frank. "You wonder if we could make any important discovery if we looked around here a bit, while Sallie is helping her ma do up some fruit jars or something like that?"

"Perhaps it wouldn't be just the right thing," suggested Andy, in confusion.

"Under ordinary conditions it certainly wouldn't," his cousin went on to say; "but when you've got a pretty good idea that you're dealing with a slippery hobo, actor, past-aviator, and now a bank burglar and cracksman in general, why that puts a different face on the matter, don't you see, my boy?"

"All right; let's take a look," said Andy, easily convinced that since they were really working hand in glove with the police authorities, they had a perfect right to prowl around in anybody's room, and pick up such valuable information as could be found afloat.

But after all they found nothing that looked like incriminating evidence. The fact of the matter was that the professor did not seem to own any sort of wardrobe whatever, and had nothing belonging to him save the clothes on his back, the little case of butterflies which Frank believed he had bought for a dollar over in Cranford at the curio dealer's shop, and a few bottles holding some strong smelling acids, which possibly were used to either kill the captured butterflies so they would not beat their wings out; or else to preserve certain specimens of bugs he expected to run across in his hunts.

"Nothing doing," said Andy, with considerable of disgust and disappointment in his voice.

"Come here!" remarked his cousin, softly.

"Hello! don't tell me you've found something?" and Andy crossed the floor in more or less haste.

He found Frank bending over a table at which there were writing materials—pen, envelopes, paper and a blotter.

"What's doing? Have you found the gentleman's notebook lying carelessly around, and which we can peep into, eh, Frank?"

"Not at all," came the reply. "I was only looking at this blotter."

"Whatever is there funny about that?" demanded the other, in puzzled tones, as he glanced first at the object in question, and then up at the face of his chum.

"It was a new one, or nearly so, you see! and somebody has been writing heavily, and then pressing the blotter over it," Frank went on.

"And if you could read backwards now, you might make out what they said; is that it, Frank?"

"Oh! that part is as easy as falling off a log. I held it up to the looking glass here. See if you can make it out, Andy."

Hardly had the other looked than he started to read, interjecting remarks of his own as he proceeded.

"Some words missing, looks like, Frank; let's see; 'Car on siding----'rive at 11 P.M. Wed. He says keep low, and trust to him—throw—track. Mum.' That's all I can make out, because he didn't sign any name, it seems. Whatever do you make of all that stuff, Frank?"

First of all Frank pulled out a pencil and copied the marks upon a piece of paper, which he thrust into his pocket.

"He might miss the blotter if I cribbed it, and take the alarm," he explained, as he hastened to put the article in question back on the table, lest Sallie come in at any minute and discover what they were doing, taking liberties in the room of the boarder; and then she would have to be told everything, which might work out badly, Frank feared.

"But I reckon you've got some sort of idea what that writing means, Frank?" pursued the other Bird boy, who, once he started on a subject could no more be shaken off than a bulldog.

"Of course I have, and it's given me something of a shock, too, let me tell you, Andy. First of all, you may know that this very day is Wednesday."

"The day he mentions there; to be sure it is. But Frank, can all this have some reference to another crime they mean to commit?"

"I'm afraid it does," came the reluctant reply.

"Tell me what he means by 'car, siding, track, mum,' and all that. Of course I can understand that he warns the fellow he's sending the message to to keep quiet. What car can he mean? Do you think they aim to steal some one's expensive car now—that they've gone and wrecked Percy's biplane, and must have another means for getting away?"

But Frank simply shook his head at that.

"Oh! you're away off your base there, Andy. He speaks of a car on a siding, and that can only refer to a railroad car. Now, I happen to know that they expect the pay-car to be along some time today or tonight, and it always lies there on that Jeffreys Siding, until they've passed out thousands of dollars to the men who call Bloomsbury their headquarters. Do you see now what it must mean, Andy?"

Andy gasped, and then exclaimed.

"Once more you've gone and seen through the riddle that knocked me silly, Frank. That's just what it must mean—the pay-car would offer fat pickings, all in cash; and they've held up their flight to Canada just to try and gobble it. Oh! what a slick game, with Todd giving false information, and perhaps just leading the police further and further away from Bloomsbury tonight, so as to leave the pay-car next to unprotected. Yes, and doesn't he go on like this, 'he says keep low, and trust to him'? That must mean Todd, don't you think?"

"I read it that way," replied his cousin tersely, as he rubbed his chin in a reflective fashion; for they were now grappling with a dangerous problem, and Frank was only too well aware of the fact that a slip might upset all calculations, as well as possibly endanger their lives; since they were dealing with reckless men, and no boyish rivals like Percy Carberry and Sandy Hollingshead.

"Do you think this was meant for the other one of the bank thieves?" Andy went on to ask.

"It could hardly have been for any one else, Andy. There must have been more to the letter, but the rest dried before he blotted it."

"And that fellow is in hiding somewhere, perhaps watching the biplane, and ready to fight before letting it be retaken, because they depend on it for their get-away to the great lakes and Canada;" Andy further observed.

"Yes, just as you say," the other remarked.

"And now since we've learned this much, Frank, what are we going to do about it—try and find where the stolen biplane is, and do something so as to make it no good for their purpose; or just slip away, go round a little like we were just out for a spin, and getting back to Bloomsbury, put them wise?"

"Neither, just yet anyhow," the older Bird boy remarked. "Not the first, because it would be taking big chances, if, as we believe, one of the robbers is concealed near where the stolen biplane may happen to be lying, partly hidden with dead leaves, so it couldn't be noticed from above; and he would be apt to do something we'd find unpleasant. And as for going back and telling, we'll have to be mighty careful there."

"And why, Frank?"

"Well, to begin with, even the walls have ears, they say; and if the police were suddenly called back from their hunt to the southwest, the fact might get to the robbers; and you know what would happen then."

"Oh!" said Andy, shrugging his shoulders, "I suppose they'd just throw this second job up, and cut stick for Canada, as fast as they could make the aeroplane spin, which would be too bad for Chief Waller, and Joe Green, and the rest of that bunch at Headquarters, who are already figuring on how they'll spend their reward money they hope to get when the bank pays for rounding-up the two thieves."

"But, perhaps, if we just told our fathers, Andy, they might get a few bold men together and lay a beautiful trap for the fellows so that when they broke into the pay-car, they would be made prisoners."

"Bully idea, that, Frank, and I hope you decide to carry it out. Just to think what a pleasant surprise it would be for our butterfly collector, expecting that he was going in to gather in another lot of plunder, and then to hear a voice say to him: 'Hands up! you're our prisoners!' Oh! wouldn't I like to be Johnny-on-the-spot when that happens. Wonder if they wouldn't let us have a part in the proceedings, after we brought the news that upset the plans of the yeggmen?"

"That will do for just now, Andy, because here comes Sally again. Let's be gaping at the wonderful collection that almost cost the professor his very life in all sorts of hot countries, as well as a whole pocket full of money—if you don't care what you say."

And when the farmer's daughter did enter the room a minute later, she saw the two boys standing there, a rapt look of admiration and envy on their faces, as they stared at the little case of common local butterflies which possibly some boy had gathered together, and then disposed of for a song.

While the young aviators had in this fashion about decided on their plan of action, they saw no reason for any hurry. The day was still long, and when they felt like starting toward home it would take them but a very short time to get there.

Meanwhile, there seemed to be some sort of fascination holding them to the neighborhood of the Hoskins' farm. And when they went away a little later it would be with the idea of hanging about, and seeing if the odd little professor might not come along. Both of them thought they would like to look at him. The man who was capable of playing such a clever game as this must surely be worth seeing.

Then again, the fact that Casper Blue once upon a time had been a daring birdman had something to do with this interest on the part of Frank and his cousin, because there is always a certain fellow feeling between those who are engaged in the same dangerous pursuits. But possibly Andy on his part was hoping secretly that by spying around they might be able in some way to learn where the yeggmen had hidden the plunder they had taken from the looted Bloomsbury bank.