In a dusty corner of a basement in a rambling Victorian house in northern New Hampshire, a door has long been sealed shut with 39 six-inch-long carriage bolts.      The home's new owners are Chip and Emily Linton and their twin ten-year-old daughters. Together they hope to rebuild their lives there after Chip, an airline pilot, has to ditch his 70-seat regional jet in Lake Champlain due to double engine failure. The body count? Thirty-nine.        What follow is a riveting ghost story with all the hallmarks readers have come to expect from bestselling, award-winning novelist Chris Bohjalian: a palpable sense of place, meticulous research, an unerring sense of the demons that drive us, and characters we care about deeply. The difference this time? Some of those characters are dead.