In many of the deep pools of the streams and rivers guardian-demons were believed to reside， and it was dangerous to bathe in them. Sometimes， when a castle or mansion was being sacked， a faithful servant or two contrived to rescue the plate chest， and to cast it into a deep pool in the nearest stream. On one occasion a diver was got to got to the bottom of such a pool to fetch up the plate of the neighboring castle. He dived， saw the plate chest， and was preparing to lift it， when the demon ordered him to go to the surface at once， and not to come back. At the same time the demon warned him that， if he did come back， he would forfeit his life. The diver obeyed. When he reached the bank he told what he had seen， and what he had heard. By dint of threats and promises of large reward， he dived again. In a moment or two afterwards his heart and lungs rose and floated on the surface of the water. They had been torn out by the demon of the pool.