He went to search for him, and finding that the boy had not passed Maka, who was on watch, he concluded he must have gone to the lake.

There was no reason why the restless youth should not seek to enliven his captivity by change of scene, but Captain Horn felt unwilling to have any one in his charge out of sight for any length of time, so he went to look for Ralph.
He found no one on the rocky shelf.

As there had been little reason to expect a water attack at this hour, Mok had been relieved from guard for a meal and a nap.

But as Ralph was not here, where could he be?
A second glance, however, showed the captain the boy's clothes lying close by, against the upright side of the rock, and at that moment he heard a cry.
His eyes flashed out toward the sound.

There on the other side of the water, sitting on a bit of projecting rock not far from the great opening in the cave, he saw Ralph.