Nancy Drew 48: the Crooked Banister

Nancy and her friends Bess and George spend an exciting week exploring a mysterious zigzag house with its fantastically crooked staircase, its bizarre serpent picture, and an unpredictable robot that nearly causes the young detective to lose her life. But despite the threat of danger from the robot, Nancy is determined to solve the mystery of the weird house and to locate the missing owner, who is wanted by the police.