President Abraham Lincoln's top spy is a bodyless head known only as Screw-On Head. When arch-fiend Emperor Zombie steals an artifact that will enable him to threaten all life on Earth, the task of stopping him is assigned to Screw-on Head. Fortunately, Screw-On Head is not alone on this perilous quest. He is aided by his multitalented manservant, Mr. Groin, by his talking canine cohort, Mr. Dog.