She guided me up the carpeted stairs. Where was Watson? It didn’t matter. Here was a door that she opened, almost clumsy with eagerness. Here was the soft, cozy darkness of a bedroom, a four-poster bed draped in glossy damasks. It was as elegant and homey as the rest of the house, with a heavy, old-world glamor. A single bedside light burned gently.

“Sit, here. Stay still.”

She lowered me gently onto the edge of the bed. I sat trembling, aware of my body in a ...