The game had the same essential concept of the comic book, although it altered the personalities of Hobgoblin and Gremlin, initially the good monsters but now appeared as villains, to the extent that Gremlin was a boss.
Warlock, wanting to have power and rule over all the other monsters, creates a shrinking spell to use as punishment for any who chooses to oppose him. As time goes on, all of the monsters choose to join his side – except for Vampire and The Monster. However, the spell was miscast – causing all of the monsters to shrink in size. Warlock sends out his henchmen, led by Spring Heeled Jack, Bigfoot, Kraken, Gremlin, and Medusa while Vampire and The Monster are watching TV in the Miles home. They must fight their way through the upstairs and kitchen of the home, the street, and the sewer; they emerge in a construction site and an Orientalist garden before fighting Warlock at Monster Mountain, although that is not the end of the game.
Vampire and the Monster’s abilities in the game are the same (though 2-player simultaneous action was an option): they can make an attack that can extend slightly beyond their bodies with a bit of a blaze, and they can make a double jump from the height of their jump, something that has since become a common move in many video games.
The remaining good monsters from the comics—Werewolf, Vampiress, Golem, Swamp Beast, The Phantom of the Opera, Jotun Troll, Invisible Man, Dr. Jekyll, and Mummy—made no appearance whatsoever in the game, although Werewolf did appear on the cover. Warlock and Minotaur were the only two monsters from series 2 to appear in the game. In the comic book, however, Medusa declared that by her count, Vampire’s side had a majority, though all the other series 1 monsters were included as enemies in the game