Sophy tried to follow, but there were many intersecting paths or tracks in this part of the woods, and she was not in the least sure which one her brother had taken. She ran along one, only to find that it was rendered impassable by some brambles, so she turned and went back to her starting-point to try another. She hoped that she should not again hear that terrible cry. It might be an owl, as Peter had suggested, but then again it might not. Peter did not really know for a certainty what it was. And then, as suddenly as it had come before, rang out once more this unearthly shriek. Sophy covered her face with her hands for an instant. Then, indifferent as to what might become of her if only she could get as far as possible from this terrible creature, whatever it might be, she fled in the opposite direction to that from which the sound appeared to come. Peter and Sirius pursued their way with unerring instinct to a large tree, upon the unleaved branch of which sat an immense owl. What had at first disturbed it Peter could not guess, but at his approach the owl gave another cry and then, spreading its wings, flew aimlessly away into the deeper woods, flapping blindly among the trees as it went. It was unusual to see an owl so active in the daytime, and Peter, his naturalist’s nature all alive, followed closely, anxious to see what would happen next. He stopped long enough, however, to try to discover what had frightened the bird, but could find nothing. Then he concluded that the enemy, whatever it was, must have disappeared. It was a great horned owl, he was almost sure, and he knew that one of that species was rarely seen so near civilization. He followed it as closely as possible, but during his short stop to look for the cause of its fright the owl had disappeared, and Peter did not see it again. After spending some time in a fruitless search for it, he returned to the edge of the wood, supposing that he should find Sophy where he had left her; but his thoughts were now distracted by something else. The excited barking of Sirius proved that he had come upon prey of some sort, and sure enough, when Peter reached the dog he saw that he had discovered the entrance to a nest of field mice beneath an old log, and already he had killed one of the parents. Peter hoped to be in time to save the other, but he was not, and scarcely liked to scold Sirius for the double murder, for he knew the dog was only following the instincts of his kind. He determined to secure the young ones, however, if young ones there were.