Borrower of the Night (Vicky Bliss 1) by Elizabeth Peters
A missing masterwork in wood, the last creation of a master carver who died in the violent tumult of the sixteenth century, may be hidden in a medieval German castle in the town of Rothenburg. The prize has called to art historian Vicky Bliss, drawing her and an arrogant male colleague into the forbidding citadel and its dark secrets. But the treasure hunt soon turns deadly. Here, where the blood of the long-forgotten damned stains ancient stones, Vicky must face two equally perilous possibilities. Either a powerful supernatural evil inhabits this place . . . or someone frighteningly real is willing to kill for what Vicky is determined to find.