What starts as a childish prank for her father's affection turns into a deadly game of cat and mouse for 16-year-old Mia when she discovers her beautiful new stepmom Suzanne's secret possessions: an address book, a stash of money and a knife caked in blood. Mia makes the fateful mistake of phoning Daniel, a murderer from Melanie's past, who believes he's possessed by a demonic silverfish. And at midnight, on the boardwalk of a sleepy seaside town, Mia's survival will depend not only on whether Suzanne is good or evil, but whether Mia can find out which before Daniel reaches them.