This is the copy I have, acquired sometime in childhood. What's interesting about it is that there's no indication anywhere on the exterior that it was published as a children's book.
The inside blurb pages make reference to the book's Newbery-winner status, but there's no gold medal on the outside (unlike the Laurel Leaf edition you'll find in most bookstores now).
Here's the back cover text:
"Prisoner in a House of Strangers(We'll just ignore the comma splice in the penultimate sentence. Or at least try very hard to do so.)
The sunshine and laughter of childhood seemed centuries and worlds away as Kit Tyler viewed the forbidding New England coast. The lovely young woman had been raised amid luxury in the Caribbean, but now she was an orphan, unloved and alone, dependent on relatives she had never seen.
Awaiting her in the bleak dwelling that was her new home were suspicions and loneliness. The master of the house despised everything about her. The man, who claimed he loved her, abandoned her to the circle of terror. And there was nowhere to turn, no one to help, no way to escape the evil claiming her as victim..."
And on the front the book is described as "A spellbinding novel of suspense and romance..."
There's no reference to the fact that it's historical fiction (well, the cover image suggests it, but the dress is hardly accurate to the setting), and no indication that it was intended as a children's book. A potential reader could quite reasonably expect to pick up a category romance based on the signals Bantam's marketing department chose to send.
It's still the same story -- one that, apparently, could just as easily have been written for adults.
Deep thoughts aside, I think it's time to enjoy the 90-second version: