A cutscene begins the game. It shows Mario and Luigi, who decide to go to Raccoon City's finest hotels between September 26th and October 1st, 1999. (Which is actually impossible since they were both fighting in the Videogame Wars at the time.) They arrive at the first hotel. As they are about to leave, a hoard of zombies busts through the front door. Then they fight the zombies. After that, they go to another hotel, and find a note from Bowser. It said, "Dear pesky plumbers, Slender Man has come to Raccoon City. Beware, if you look, it takes you. The only way to defeat him is by assembling the enclosed instruction book." So, during the rest of the game, they search all of the city's hotels, looking for lotsa instruction book pages. They encounter Slenderman several times throughout the game. In the end, they escape to safety before the town goes BOOM!
This game is a survival/horror game. There are many attacks and weapons to chose from, most of them are guns, although, there is hand to hand combat as well. The best attack is the "Super Slendermen Take Down!" which is preformed by mashing lotsa buttons.