context: Thursday the 12th: Waldemar (Jeffrey Tambor) and his wife Yolanda (Nancy Lee Andrews), two vampires from Transylvania, are just about to close the deal on a house in Erie, Pennsylvania when they learn that it has been inherited by a family of four who are moving in as the two vampires stand there discussing the deal with the realtor.John (Richard Benjamin) and Mary (Paula Prentiss) are at a will reading where John's recently diseased uncle has left them the house as part of his will. Upon arriving at the old house John and Mary love the look of it, even though it does need some work and is rumored to have a curse on it, but their kids, 16-year-old Debbie (Kari Michaelson) and 12-year-old Billy (Kevin Brando), don't share the enthusiasm. Not even Rover, the family dog, wants to come inside. "You'll be amazed at what some nice curtains will do for this house," Mary assures her family.That evening, bored with television (all channels seem to be showing "The Twilight Zone"), Billy looks through some of the old books in the library. "The Book of Evil" looks interesting and, although the inscription warns, "Whoever shall open this book releases into the world all the evil herein," Billy begins turning the pages. Each page reveals a picture of a monster that suddenly disappears from the page. Later, as they try to sleep, Billy is awakened by a monster in his bedroom, Mary is bitten by Waldemar, and the whole family is kept up by "owls" banging and shrieking in the yard. Watching from their car, Waldemar and Yolanda are dismayed when they see monsters and realize that someone must have found THE BOOK.Friday the 13th: John and Mary go shopping (for curtains), Billy discovers that his mom has cleaned his room and moved THE BOOK. Meanwhile, Debbie takes a bubble bath and is scared silly by the fin floating in her bathwater which rises to reveal a 'gill-man' creature, who chases her, but instead kills a local delivery guy.Later that day, Mary is attacked by a horde of bats in the attic (shades of 'The Birds'). As a result, they family decides to call an exterminator. The exterminator, Mr. Van Helsing (Severn Darden) assures the family that he can cure their bat problem and moves in ("You don't expect to get rid of bats overnight!"). Over dinner that night, Billy admits to having found, opened, and lost THE BOOK, and Van Helsing warns the family that the world is in grave danger if THE BOOK is not found.Saturday the 14th: John and Mary have planned a party for the relatives and a few friends. The guests start arriving, but Billy has come up missing so everyone goes looking for him. At one minute to midnight, Waldemar and Yolanda come calling with Billy and THE BOOK in tow. As the monsters approach from all sides, Van Helsing pleads with Billy to hand over THE BOOK, but Billy refuses. It seems that Billy has seen a picture of Van Helsing in THE BOOK and that Van Helsing is really one of the monsters, too. Van Helsing and Waldemar make faces at each other in attempts at a powerplay. Suddenly, Van Helsing grabs THE BOOK from Billy and disappears along with all the monsters. Instead of THE BOOK's destruction freeing all the monsters, destroying THE BOOK destroyed all the monsters along with it.In the final scene (set on Sunday the 15th) John, Mary, Debbie, and Billy move out and away from the old house and the vampire couple of Waldemar and Yolanda move in.
question: What does Waldemar and Yolanda want that is in the house?
answer: The Book