Strother Martin and Dirk Benedict star in this eerie tale of a respected snake expert who masks a frightening desire to transmute a man into a king cobra. Realizing that his new lab assistant, David (Benedict), is the perfect specimen, the demented doctor begins administering to him injections of "immunization serum." Soon, David begins experiencing strange and disturbing side effects: his skin is shedding while his body shape is changing. But before he realizes the horrible truth, the metamorphosis from human to serpent has begun.