From Strategyinformer.com: "The Unknown Menace has its very own story and challenge, but like most creations, it took inspiration from other games and mods. The Unknown Menace took nothing from the storyline of Half-Life, and is completely independent from it, although the user will have to possess the game to play the mod, because it uses some sprites, models and textures from it, that wont be featured in the pack."
