Bess and George were always interested in observing Nancy's sleuthing procedures. They often wondered whether it was her charm, her straight-forwarded manner, or her businesslike approach that unfailingly gained her entrance to offices of officials. p.43This time Nancy is asked by her father to investigate an adoption and/or kidnapping case that happened many years before as related to a new case of his. This leads Nancy to a quaint town with a castle (for whatever reason) and another case about moonstones which, of course, leads back to the first case all wrapped up in one neat package.
The Phantom of Pine Hill (Nancy Drew Mystery Stories #42)
For several seconds Nancy did not move. There had been a few times in her life when she had been utterly confounded by some event which seemed to hold no explanation except a supernatural one. This was one of those times. p.34When a mix up at the hotel results in Nancy, George, and Bess staying with an elderly gentlemen for their visit to Emersen University June Week, it also leads to a mystery for Nancy and her crew. The mystery involved a phantom who breaks into Uncle John's, the elderly man, library without any means of entering or exiting. It's up to Nancy to solve that and another mystery that comes along involving sunken treasure.