In 1955, ten-year-old Lewis Barnavelt goes to New Zebedee, Michigan to live with his uncle Jonathan in a creaky old house which has a mysterious ticking heart. Recently orphaned, Lewis only wants a normal childhood but soon discovers he is in line for anything but that. Uncle Jonathan is a well-intentioned warlock and his next-door neighbor and good friend, Florence Zimmerman, was once a far more powerful good witch. Jonathan’s house was previously owned by Isaac and Selena Izard. Before dying, this sinister couple had constructed a powerful clock that is hidden somewhere within the house’s walls, ticking eternally to pull the world into a magical alignment that would permit Isaac to cause the end of the world. When Lewis, wanting only to befriend and impress his popular classmate, Tarby Corrigan, attempts to raise a dead person in the local cemetery on Halloween, he accidentally releases the evil warlock, Isaac Izard, from his tomb. Things quickly go awry as Izard moves to recover the key and set the clock in motion to end the world. Now, Lewis, Jonathan, and Mrs. Zimmerman must summon all their courage to defeat Izard.