"No. It takes many minutes to enter a body like yours without giving warning. The openings in your skin are large, but my body is much larger. If you let go of the other person's hand while I was still partly in both bodies, it would be very embarrassing for all concerned. If I left you entirely and worked at night while people were asleep, I suppose I could cover the whole island eventually; but I would be very much restricted in speed, and would be in an extremely awkward position when I found him. I will undoubtedly have to make the final check that way, but I should very much like to be pretty sure of my ground before testing anyone. I still want your ideas."
"I don't know any of your standard methods," Bob said slowly. "And I can't, right now, think of means for checking people for company} but we might try to trace his course from the time he landed, and find what people he might have got at. Could that be done?"
"With the addition of one word, yes. We can trace his possible course. There is likely to be little or no evidence about his actual path, but I can judge, I think, with considerable accuracy what he would do in any given situation. Of course I'11 have to know a lot about the situation: all you can tell me, and all I can see for myself."
"I can see that," answered Bob. "All right, we'll have to' start with the time he reached the island-if he did. Any ideas?"
"We'll have to start sooner than that. Before we can guess where he landed, we must judge where he crashed. Will you point out on your map the place where I found you?
Bob nodded, and his finger indicated a point on the paper. At the northwest tip of the island-the end of the longer branch of the L-the land tapered to a blunt point; and from this point the reef extended, first northward and then curving to the east and back to the south to enclose the lagoon. Bob was indicating the west side of this point.
"This," he said, "is the only real sea beach on the island. It's the only part of the shore not protected by the reef.
You see south of the tip there's a few hundred yards before the reef starts again and keeps the breakers from the whole south shore. It's the place the fellows and I like best, and it's where we were swimming the day you arrived. I remember that shark."
"Very well." The Hunter took up the conversation. "Up until shortly before we reached the earth's atmosphere I was tracking him on automatic control, so that I was within a few feet of his line of flight When I realized how close we were to the planet I went on manual and tried to drive straight away, but it was along the same line. Even allowing for the disturbance your atmosphere caused on our lines of flight, I don't think we could have struck the water more than a mile or two apart. I can check that; I was watching him on the bow scanner, which has only a ten-degree field of vision.
"Also, I could not have crashed far offshore. Do you know how rapidly the water deepens off the island?"
"Not in feet. I know it's steep, though; large ships can come quite close to the reef."
"That's what I thought; and I was in shallow water. We crashed, we will say, within a two-mile radius of this point." The Hunter momentarily shaded, on Bob's retina, a point a little way off the shore from the beach. "And much of that can be eliminated. He certainly did not crash on shore; my instruments showed him sinking after the initial check. I am equally sure he did not land in the lagoon, since you say it is very shallow, and he must have struck hard enough to reach its bottom instantly-at a guess, he must have had over fifty feet of water; I certainly did, though not much over, I should say.
"We can, then, act on the assumption that he landed in the two-mile semicircle to the west of the island, centered just off-shore from your beach. I admit that is not an absolute certainty, and it may be hard to prove, but it gives us something to start on. Have you any other ideas?"
"Just questions. How long would it have taken him to get ashore?"
"Your guess is as good as mine. If he had the luck I did, a few hours. If he was in very deep water, with even less oxygen than I, and a stronger sense of caution, he might have spent days or weeks crawling along the bottom to shore. I myself would never have attacked that shark, or ventured to swim out of touch with the bottom, unless I had been very sure I was near shore."
"How would he have known the right direction? Maybe he's still crawling around down there."
"Maybe. However, with the storm that night he could have determined the direction of the breakers as easily as I did; and if the bottom slopes as steeply as you think, it would have furnished another clue for him. I don't think that problem would have been serious. Of course he is known to be a coward; that may have kept him with the wreckage of his ship for quite a while."
"Then in order to go any farther we'll have to explore the reef for a mile or so each way from the beach, to see if he left any traces. Is that right? And if he has, what do you suppose he will have done after landing-same as you?" "Your first guess is right. As for the question, that depends. He would certainly want to find a host as soon as possible; but whether he simply waited for one where he landed, or went in search of something suitable, is hard to say. If he landed at a spot where any artificial structures are visible, he would probably have made his way to them, on the theory that intelligent beings were bound to come to them sooner or later. It's something that can't be predicted exactly, that's why I said I would have to know all the circumstances to guess his actions."
Bob nodded slowly, digesting this. Finally he asked, "What sort of traces are you likely to find at his place of landing? And if you don't find any, what will we do?"
"I don't know." There was no indication which question was being answered; and Bob finally grew tired of waiting for further explanation. It bothered him, for even he could see that the methods they had just outlined were not very promising. He thought intently for a time, half hoping his guest would come out with some supplementary technique from his own science. Suddenly an idea struck him.
"Hunter! I just thought of something! Remember the only time you could get to me, that day on the beach, was when I fell asleep?" The alien expressed assent. "Well, won't the same be true of this other fellow? He couldn't catch a person, or at least couldn't do it without being seen. You said yourself that it would take several minutes to get right inside; and even if this fellow doesn't care about the feelings or health of his host, he still wouldn't want to be seen. So it ought to narrow things down a bit if I found out who had been sleeping near the water in the last few months. There aren't any houses near the sea -Norm Hay's is the closest, and there shouldn't be too many people who made picnics the way we did that day. How about it?"
"You may have a point there. It is certainly worth trying; but remember, there is no part of the island that he could not reach given time enough, and everybody sleeps at some time or other-though he mightn't know that, come to think of it. Certainly anyone who has slept near the shore is, as you say, suspect"
A change in the rhythm of the engines interrupted the thoughtful silence that followed this remark, and Bob went back on deck, to find that the tanker had slowed and was turning to line up for the entrance to the western passage through the reef. A hasty trip along the catwalks took them to the bow, from which an unobstructed view could be had of the north reef and lagoon.
The reef, it seemed to the Hunter, was not too encouraging a field of search. Certainly no human being could have hidden there for long; and while his quarry could undoubtedly remain concealed, life in such a place would not be pleasant. Long sections of the barrier were barely visible above water, their position betrayed mostly by the breakers. Some portions were higher and had accumulated enough soil to support sparse vegetation-even coconut palms in one or two places. As the tanker nosed into the narrow passage, he realized that, in spite of this, searching the reef for clues might not be easy; it was never possible for a person to travel more than a few rods on foot, as he could see from the broken-up nature of the barrier; and on the outer side at least boating would be extremely dangerous-the endless breakers crashing through the openings in the coral created fierce and unpredictable currents and eddies almost certain to sweep any small craft against the rock-hard roughness of the reef. Even the tanker, big as she was and with plenty of steerage way, kept to the center of the marked channel while Bob and the Hunter watched the coral slip by on either side.