“what was the matter?” gasped frank, somewhat dazed, as he crawled away and sat up. “why did you shove me over?”

“don’t you see?” asked andy quickly. “he was going to hit you! then he’d have tackled me i guess. look out! he’s at it again!”

with a snarl of rage the man had again raised the club. but frank was too quick for him. fairly leaping at him, the sturdy lad tore the piece of driftwood away and tossed it some distance off.

“so! that’s how you keep your promise, is it?” the elder lad asked. “we won’t give you any more chances. we’ll tie him up again, andy, and let him go hungry for a while.”

the man glared hatred at them, and tried to fight them with the hand they had freed so that he might eat. but the two lads were more than a match for him in his condition, and soon had him made fast again. he had eaten only a part of his dinner when he thought he saw this chance to make his escape.

“are you going to leave me like this?” he growled, when andy and frank resumed their interrupted meal. “i’ll get sunstruck.”

“it would almost serve you right,” murmured frank, “but we’ll return good for evil. let’s make a sort of shelter, andy.”

with pieces of driftwood they raised a framework over their prisoner as he sat on the sands. on the boards they put sea weed, of which there was an abundance, and soon the man was sheltered from the hot sun.

“we’ll have to make something like that for ourselves to-night,” observed frank.

“yes, and it isn’t going to be very pleasant staying here with that man, even if he is tied up,” went on his brother. “i’m afraid he’ll get loose in the night and attack us.”

“we’ll have to look well to the knots, and keep a sort of watch i suppose,” remarked frank. “but let’s go back and finish searching in that wreck. i wonder what it is that’s in it, and where it is?”

but the boys found no answer to their questions, though they made diligent search.

“i don’t believe it’s here,” said andy at length. “whatever there was paul must have taken away before he lost his memory, and he may have hidden it somewhere else. but i have another plan, frank.”

“no jokes, i hope.”

“no, this is serious. the more i think of staying here with that man all night, the less i like it.”

“i don’t like it either, but what can we do? dad may think we’re staying away too long, and he may come for us. he knows we started for cliff island. then again he may not come for several days, as he knows we’ve got lots of food. and our distress signal doesn’t seem to attract any attention.”

“no, and that’s why i think we oughtn’t to stay here any longer. it is very seldom that vessels come here, and we haven’t much chance of being taken off. we ought to get away and in the path of the fishing schooners. then we would be picked up.”

“yes, but how are we going to get off? we haven’t a boat.”

“i know, but we can make a raft. there’s no end of wood here, and we have plenty of rope left after tying that man up, with which to bind the planks together. there are some nails in the motor boat wreck, too, and some tools. we could make a raft good enough to take us far enough out so we would be picked up. we might even make the main land. there are two paddles in the swallow.”

“what are we going to do with him—leave him here?” and he nodded toward the prisoner.

“we’ll have to take him along,” said andy. “we’re not going to lose him after we had so much trouble in finding him.”

“well, perhaps it’s the best thing to do,” agreed frank, after thinking it over. “but we can’t get it done in time to leave to-day. it’s late afternoon now.”

“no, but we can start it, finish it the first thing in the morning, and leave as early as possible. we ought to be home by to-morrow easily.”

“i wish we could be. if we could only run the swallow!”

“it wouldn’t be safe, in the condition she’s in. the raft is the only thing.”

they ceased their useless searching of the motor boat, and began gathering large pieces of driftwood. their prisoner in his seaweed shelter watched them curiously.

“what are you up to now?” he asked in his surly voice.

“you’ll see soon enough,” answered frank. he had no idea of telling their plans.

it was not so easy to build a raft that would hold three as andy had supposed. but they did manage to get the framework of it together. then they had to think of a shelter for themselves, and built one near that of the prisoner. they also gathered wood for a campfire and made preparations for supper.

“am i going to starve?” demanded the man, as they made no effort to loosen his bonds so that he might eat. “i’m thirsty, too.”

“we’ll feed you and give you a drink,” spoke frank. “we aren’t going to take any more chances.”

and this they did, putting pieces of food in the man’s mouth, and holding up a tin cup for him to drink from.

they divided the night into watches, each taking turns. while one slept the other would sit by the fire to see that the desperate man did not loosen his bonds.

it was andy’s trick, and he was very tired. in spite of himself his head would nod at times. he even walked up and down to get rid of the sleepy feeling but it came back. as he sat by the fire his head swayed to and fro.

“i’ll just close my eyes for a half minute,” he told himself. “just for a few seconds. i—i’ll—”

andy was asleep and in the shelter where the prisoner lay bound there was a movement. eager and cruel eyes watched the lad on guard. both andy and frank were slumbering now.

“it’s my only chance,” murmured the man as he heard their heavy breathing. “my only chance.” then he began rolling over and over on the sand, out of his shelter.