Beware of ouija boards, vampires and unexpected guests in the 21st annual installment of the "Treehouse of Horror." In "War and Pieces," the first of three spine-tingling tales, Marge, worried about the effects of excessively violent video games, encourages Bart and Milhouse to give wholesome, classic board games a shot. The best friends discover that board games aren't boring after all when they find themselves playing a real-life game in which they must beat all the challenges before they are allowed to return to home. The supernatural spells continue in "Tweenlight," when Lisa becomes smitten with a mysterious new student, Edmund, who also happens to be a vampire. When a romance blossoms, the young lovers run away to Dracula-la Land, leaving Homer to come to Lisa's rescue. In the final frightening fable, "Master and Cadaver," Homer and Marge set sail on a romantic second honeymoon, but are interrupted when they rescue Roger, a castaway who escaped an attempted poisoning on his ship. Convinced that Roger is sabotaging their getaway and plotting a murder of his own, Homer and Marge take matters into their own hands.