The Dark Legacy

You have received an invitation from Alfred Pietsch. A quiet comrade and the local pharmacist. Somewhat puzzled, you have become curious and finally follow the enclosed directions. Gradually, you are moving further and further away from the city, until you come to a forest, where the thicket of trees becomes more and more dense the deeper you go. Just as you think you can't go any further and it's so dark, the outlines of an apparently abandoned forest hut appear before you. What does Mr. Pietsch want and why were YOU specifically invited here? Are YOU brave enough to follow the invitation?