Piece of My Heart by Alafair Burke and Mary Higgins Clark EUC

Television producer Laurie Moran and her fiancée, Alex Buckley, the former host of her investigative television show, are just days away from their mid-August wedding, when things take a dark turn. Alex’s seven-year-old nephew, Johnny, vanishes from the beach. A search party begins and witnesses recall Johnny playing in the water and collecting shells behind the beach shack, but no one remembers seeing him after the morning. As the sun sets, Johnny’s skim board washes up to shore, and everyone realizes that he could be anywhere, even under water.