Needle

It was rapidly growing dark now, and the only conclusion reached by the boys was the obvious one that nothing much larger than insect life had disturbed the dog's body. No one had actually touched the bones as yet, but with seeing growing more difficult by the moment Malmstrom decided to get a closer look. The skull was inside the thicket, but it was this he chose to examine, and he reached very gingerly among the thorns to pick it up.

Getting in gave little trouble, but it developed that the thorns on the short side branches pointed back in toward the main stems. This furnished about as efficient and unpleasant a trap as one could well hope not to encounter, and Malmstrom picked up several very nasty scratches as he withdrew hand and skull. He handed the latter to Colby and shook the injured member.

"There's something that would make a good fish spear," he remarked. "The darned thorns fold back against the branches easily enough, but they spring out again when you pull the other way. I bet that's what happened to Tip -he chased something in here and couldn't pull out."

The theory was a reasonable one, and even Bob was impressed, by it. He suddenly remembered that he had not told his other idea to the doctor; what would Seever's opinion be? Perhaps by now he had worked out some medical test, and there would be no difficulty for him in finding an excuse to use it. Bob had hoped to give him some line on whom to test first; now he did not know what to think. He led the way back downhill in the darkness, his brain working furiously.

Chapter XVI. PROSPECTUS

TUESDAY WENT as usual until the end of school, except for the fact that the Hunter was growing progressively more anxious about Charles Teroa. That one was due to leave the island on Thursday, and as far as the Hunter could see Bob had done nothing toward testing him or delaying his departure. There were only two more nights…

The boys, who had no such worries, departed on a search • for more boatbuilding materials as soon as they were dismissed. Bob started with them, but stopped off at the doctor's office, ostensibly to have his leg checked. Here he told in full the story of the preceding evening and of his theory; and the detective realized for the first time that his host had been working along a line of thought radically different from his own. He hastily attracted the boy's attention and gave his own views, together with the evidence supporting them.

"I'm sorry I didn't realize the trend of your thoughts," he concluded. "I remember telling you that I didn't think the dog had been killed by our friend, but perhaps I did not mention the fact that your 'booby trap* also seemed to be entirely natural. I should say that the branch was driven into the ground that way when the tree fell. Is this why you have been ignoring the matter of Charles Teroa?"

"I guess so," Bob replied. He gave a brief summary of the Hunter's silent speech to the doctor.

"Young Teroa?" asked Seever. "He should be coming to me for shots tomorrow. Have you reason to suspect him?"

"At first it was simply the fact that he was to leave the island," replied the Hunter. "We wanted to be sure before he was out of reach. However, we learned later that he had slept at least once in a boat moored at the reef, which gives definite opportunity for our quarry to get at him. He was also present when we nearly went through the drain on the dock, but that hardly involves him alone."

"That's right," mused the doctor. "We have quite a list of what you might call first-class possibles, with the whole island following right behind as slightly less probables. Bob, did nothing happen last night to give you ideas, one way or the other, about any of your friends?"

"Just one," replied the boy. "When Shorty Malmstrom pulled Tip's skull out of the thicket he got several gashes from the thorns; they bled like nobody's business. I kind of thought we needn't worry too much about him."

Seever frowned slightly, and addressed his next remark

to the detective. "Hunter, just what sort of conscience has this friend of yours anyway? Could he or would he, for example, let an injury of that sort bleed just to make someone reach Bob's conclusion-that there was no one of your race there?"

"His conscience is non-existent," returned the alien. "However, the sealing of such minor injuries is so much a habit with us that he might have done it anyway if he were there. Certainly if he had any reason to believe his host were under suspicion, and if he thought of it, he would refrain from helping him regardless of the seriousness of the injury-he is looking out for just one creature's health. Bob's point is no positive proof either way, but we can list it as a minor point in Malmstrom's favor."

The doctor nodded. "That's about what I thought from your earlier story," he said. "Well, we seem to be left with the immediate problem of testing young Teroa. It would be nice to know what yellow-fever vaccine does to your people, Hunter. He's getting a dose of it tomorrow."

"I would gladly let you find out if the stuff will not harm Bob. However, I can guarantee that our friend will simply withdraw from the limb in which you inject the stuff and wait till it attenuates. Besides, the chances of its being harmful to us are very remote. I still think I had better examine him myself. Once we locate our quarry, we can find something that will damage him."

"Once you locate your quarry, you'd better be ready with something that will damage him," retorted the doctor. "All I can offer that may do it without harming his host are a few antibiotics and vaccines; and we can't test them all at once on Bob. We should have started this business days ago." He thought tensely for a moment. "I'll tell you. Suppose we start now, one substance at a time, with the things I know will not harm Bob. You can tell us the effect they have on you-we'll arrange things so you can leave his body in a hurry until he eliminates the particular substance you couldn't stand. We'll leave testing Teroa until we find one of them that works. If none of them do, we're no worse off anyway."

"But, as you say, that will take days, and Teroa leaves this island in less than forty-eight hours."

"Not necessarily. I don't like to do it, because I know how eager the fellow is to get going, but I can hold him on the island for observation until the next visit of the boat if necessary.

"That will give us ten days, with two drugs a day, and should give us a fair chance of finding something. We'll start with antibiotics, since vaccines are usually pretty specific in their likes and dislikes."

"Very good indeed, if you are willing, Bob," was the reply. "It is a pity we did not get you into the fight before, Doctor. Shall we make one test now?"

"Sure," replied Bob. He seated himself, and the doctor draped a cloth over his legs.

"I don't know whether it's worth the trouble to take your shoes off," he said as he was swabbing the boy's arm with antiseptic. "From what I gather about your friend, he can get out if-he has to without their bothering him. All set?" Bob nodded, and Seever held the hypo syringe against his arm and pressed the plunger. The boy kept his eyes on the wall and waited for the Hunter's report.

"Just another kind of protein molecule to me," was the sentence that finally appeared. "You might ask the doctor if I should consume the stuff or if it's all right to leave loose in your system."

Bob relayed the message.

"It doesn't matter, as far as anyone knows," replied the doctor. "In fact, he would be doing me a favor if he let it go and reported any effect on your tissues to me. We believe it's harmless. Well, it's probably best not to try another today; you might as well get back to your friends. Keep your eyes open; Teroa isn't our only suspect, even if your own idea wasn't so good."