While out on a nature walk, Dr. Smith, Will and the Robot come across a strange keyhole shaped monolith beneath which sits a lyre on a pedestal. When Smith plays a few notes, he is transported to a fiery realm he believes to be hell .There he meets Morbus, whom be believes to be the devil. Morbus shows Smith his past misdeeds, and coerces him into destroying the lyre in return for passage out of hades.