The game takes place about five years after the events of Splatterhouse 2. Rick and Jennifer have since married and have a son named David. Rick has also become successful on Wall Street and has bought a mansion in Connecticut, putting the memories of the Terror Mask behind him. Meanwhile, the Mask feels the ancient energy that it recalls from ages past and begins to speak to Rick. Rick once more dons the mask and must fight the monsters that have invaded his mansion. Rick first fights to save Jennifer, who has been kidnapped by the Evil One, but it is revealed this was only a distraction while the Evil One took David.
Rick eventually defeats an entity known as the Evil One, who had planned to use David's latent psychic abilities to unlock the power of an object known as the Dark Stone. Upon defeating the Evil One, the Mask reveals its true, evil intentions. Rick must then destroy the Terror Mask permanently
Splatterhouse 3 dramatically changes the gameplay from the game's before it. Rick's environment is now much larger. The game features six levels, many taking place in the mansion. Instead of the side-scrolling action of the previous games, Splatterhouse 3 features non-linear exploration throughout several different rooms, forcing Rick to often backtrack as he tries to find the exit. Players are given a map of each level.
A timer has been introduced to the gameplay. Each level must be cleared in a certain amount of time. Although this does not affect gameplay, running out of time results in changes in the plot, creating four possible endings. By running out of time, for example, Jennifer will be killed in the second level. New to Splatterhouse is the Power Meter, which can be filled by collecting Eldritch Orbs found throughout levels and occasionally are dropped by defeated enemies. Once full, the player can transform Rick into a hulking and more monstrous version of himself with the Terror Mask being seemingly fused to his head. In this state, Rick is significantly stronger and can execute a special attack that involves pieces of his flesh extending from his chest area and acting as a weapon, injuring any monster in the vicinity of their reach. Also, instead of actually wielding the weapons he finds, the mutated version of Rick simply flings them at enemies, dealing a fair bit more damage than swinging the weapons as normal Rick would have. Extra lives and health items are also scattered throughout the levels. Passwords are also given to players to return to levels.
Occasionally, Rick is able to pick up weapons (i.e. a baseball bat or a cleaver, among others) to use against the monsters. Once you defeat all the monsters in the room an in-game map appears to give you some choice in how you get to the end of each level. The game's storyline alters significantly if you fail to finish levels before the allotted time runs out. For example; in the second level you are tasked with saving Rick's wife Jennifer from being devoured by a boreworm. In order to save her, you must reach the end of the level to confront and defeat the boreworm within the time limit. Failing to do so before time runs out will result in Jennifer being devoured internally by the boreworm planted inside of her body.
Source: Wikipedia, "Splatterhouse 3," available under the CC-BY-SA License.