The Finger of God

How do we understand the affliction of tzara'at? Why are the laws of tzara'at placed in the middle of Sefer Vayikra? By closely reading the text and noticing parallels in the story of the deaths of Nadav and Avihu, we can learn about the uniqueness of tzara'at as a supernatural affliction that comes from God, and the role of the Kohanim in distinguishing between tum'ah and tahara.