The Screamer is set in a dark futuristic environment. The existence of a megalopolis called Beast City depends on a huge complex known as "Biological Intelligence in Artificial System" (sic), usually referred to as simply "BIAS". But recently, disturbances within BIAS have been reported. Apparently, dangerous creatures have gone rampant. Nobody dares to venture inside - except, naturally, the protagonist of this game...

The game is a somewhat unusual mixture of first-person dungeon crawler and side-scrolling action. Following a simple character creation, the player is taken to the Beast City, where it is possible to rest, buy equipment for the hero, and hear the latest gossip. Afterwards, the player can venture into the depths of BIAS, which is a huge maze-like dungeon. Enemies attack randomly, however, instead of the usual turn-based battle screen, the hero and the enemy are taken to a small side-scrolling area.

At that point, the game plays similarly to a side-scrolling shooter: the hero can jump, duck, and shoot at the enemies in real time. Due to the RPG nature of the game, the outcome of the battle depends on the hero's level as well as the player's dexterity.