The shepherd and losing sheeps

Ms. Joan, an elderly woman, who has fifty sheeps, and her shepherd Jack, takes them every morning to grazing in the nearby valley. Everything went as usual until one day in the evening. Then something unexpected happened. Before going home he heard a strange metallic noise at the end of the herd. A dark container opened up by itself, headed towards the back end of the herd, closed suddenly and disappeared under the ground. Sheep fled frightened. He got scared and led the herd quickly to the house. After counting the sheeps, Jack found out that one was missing. He told her employer. She managed to thrust out the words: "Be careful or no more job for you".On the next evening, after Jack came back home, again one sheep was missing. Jack lost his job and Ms. Joan called Police regarding the missing sheeps. Jack was still at the scene and was questioned. He said that he didn't know anything about that. Several police officers with trained dogs entered the valley to search for a clue about the missing sheeps. They were there for several hours but nothing suspicious happened. One of the dogs suddenly started barking nearby. Police officers went there and began to dig. Not long after they began to dig they found a lid. One of them opened it and they went inside into a big and long tunnel with lights on. They found another door. They opened it and they saw a professor like a scientist working with a high-tech device containing a big screen with flashing lights on and off, electronic signals and diagrams moving horizontally and vertically like sinusoids and the like.