Players take the role of Amagon, who is a Marine trappd on an island as a result of a plane crash. The player must guide Amagon through the island to reach the rescue ship, defeating a number of foes-including the final boss, which is based on the "Flatwoods Monster", a rumoured space alien residing in Flatwoods, West Virginia. The original Japanese version departs from the above in that the main character is not a marine, but is instead a scientist named "Jackson" who transforms himself into his Macho-Man form using a special drug.