Tonight’s new 48 Hours, “Death in Deep Water,” revisits a cold case involving a long-deceased movie star. Actress Natalie Wood, a familiar and memorable film presence since befriending a department store Santa in 1947’s Miracle on 34^th Street, died suddenly, and somewhat mysteriously, in 1981, in what was called a boating accident in Catalina. The last people to see her alive were the boat’s captain, her then-husband Robert Wagner, and good friend Christopher Walken – and a few years ago, Los Angeles authorities reopened the case, and now have amassed enough evidence, and questions, to frame the narrative in a possibly more sinister bent.