Borrower of the Night — Elizabeth Peters

It began as a game, a treasure hunt in an old German castle. For Vicky Bliss -- tall, beautiful, and brilliant -- it was also a challenge, a chance to bring an arrogant young man down a notch or two. And all things considered, it would have been no contest.

The prize was a centuries-old shrine, carved by Tilman Riemenschneider, probably Germany's greatest master of the late Gothic. The place was the forbidding Schloss Drachenstein, where the stones were stained with ancient blood and the air reeked of evil.

The problem was that someone had targeted Vicky, and the game was soon being played in deadly earnest....