"Now come on," Mark said, opening the gate after learning the cause of his momentary alarm, and the children went boldly forth to do battle--two boys and a girl who counted on defending the island against fifteen or twenty savages. It was not to e supposed that the Indians, seeing the sentinels, would come directly across from the island; but might be expected to dart swiftly toward one or the other headlands, and therefore it was that Mark divided his small force, sending Luke to patrol the northern point, while he paced to and fro on the southern side of the harbor where it was more reasonable to suppose a landing would be attempted. Susan was to walk back and forth on the shore between the two lads. Once this division of forces had been made, the children began their vigil, on the alert for any suspicious noises either behind or in front of them, for there was yet a possibility that a force of Indians was already secreted near the stockade. No sooner had he begun to pace his beat than Mark realized to what danger the occupants of the dwelling were exposed in case the savages had already landed on Mount Desert, for the gate of the palisade was unlocked and unguarded, and then Susan was sent back to warn her mother and aunt that the entrance must be secured. When she returned to the shore it was with the report that the gate was barred on the inside, and Mary Pemberton standing close beside it in case the sentinels outside should be forced to beat a hasty retreat. Now indeed had the lad done all within his power to protect those whom he considered were entrusted to his charge, and it only remained to keep careful watch for the first show of mischief. And this came in a manner wholly unexpected, although it seemed to the young leader as if he had taken into consideration every method which might be adopted by the savages. During three hours or more the children had paced to and fro on the shore, each making certain meanwhile that the other two were on the alert, and then Mark saw a canoe put off from the harbor island, heading toward Pulpit Rock, as if to gain the shelter of that headland before coming to land. Uttering a low cry to attract the attention of his companions, he would have hurried on to the point in order to fire at least one shot before the Indians could disembark; but at that moment an exclamation from Luke caused him to gaze across the harbor, when he saw a second canoe setting out toward the northward. A moment later a third craft was paddled straight across the water, in the direction of Susan's post of duty. It seemed certain that the Abenakis understood how small and weak was the force opposed to them, and therefore, counted on bringing their bloody work to a speedy conclusion regardless of their ordinary methods of warfare. [Illustration: Mark saw a canoe put off from the harbor island.]