I Live in Your Basement! (Goosebumps, No 61)

Don't do this! watch out for that! marco's mom thinks the whole world is a danger zone. She won't even let marco play softball but marco wants to have fun, so he sneaks off to a game and that's what it happens. He gets hit in the head with the baseball bat. Now things are really getting fuzzy because when marco gets home, he gets the strangest call from someone who says he lives in marco's basement.