A sickly, elderly individual is being held prisoner in their own home by conniving ne'er-do-wells. Sound familiar? Maybe Edward Stratmeyer accidentally handed his ghostwriters the same outline two times in a row. (Watch for shades of Lilac Inn, too- they're in there if you know where to look.)
( 'You are more important to me than all the mysterious old ladies in the world!' )

 Nancy's evil twin runs amok (as if one of them wasn't bad enough!) as our young sleuth descends into paranoia, convinced that anyone caught knowing obscure facts about lilacs must be plotting her demise.
( 'John, do you know what 'blue pipes' are?' )

Nancy ruthlessly stalks this book's Character in Need, a poor, defensless orphan, and Evil Road Signs are always hindering our characters by warning them of Impending Doom. This makes Nancy PMS a lot.

( 'When we heard it was a black foreign car, we were suspicious immediately.' )

In which Nancy's father is kidnapped and MIA for half the book, yet our brave heroine somehow finds the time to go merrily gallivanting about  the countryside, ghosthunting.

( 'There are times when I'd like to thrash the man till he begged for mercy!' )

Nancy pokes her nose into other people's business for the first of many times. And this book really has nothing to do with the computer game. Her Interactive lied to us.

( The next instant, to Nancy's right, a ball of fire rocketed down from the sky. )