In year 5012 a weird creature Parasitis attacks your home planet Abadox. You, Second Lieutenant Nazal, have to penetrate his formless body and destroy it's core. Thus you'll resque Princess Maria and save your world.
This game was issued in 1990 by Milton Bradley Company. It is traditional for that time scrolling shooter. There are six levels in game: Mouth, Throat, Sanctum, Stomach, Intestine and Tube of Death - core of Parasitis. Some levels scroll horizontally, some vertically. You have to shoot aliens and pick up power-ups. Character is big and moves slowly that makes completion of some spots hardly possible if you've been killed and reborn in a bunch of enemies. Of course there are level bosses and special enemies that make your journey inside beast's body even more gross - and interesting!