Who comes to Goblin Lake to see its mysteries in "Goblin Lake"? What are his first impressions?

Goblin Lake, also known as Mummelsee, has properties that no man can truly explain, a peasant tells the soldiers. An officer whose name is Jack is a skeptic and asks the peasant to lead them to the lake capable of changing whatever is thrown in. He picks cherries on the way, using the pits to test the peasant's story, but as far as Jack can see, there are no changes.