She cooed, which didn’t explain anything. “Restless to be home,” Tom suggested, which is what I’d thought yesterday, but she hadn’t been this agitated last night. I supposed there was no harm in letting her out. When we entered the courtyard, I released her. She flapped her wings and flew off into the sky.

The Banqueting House was across the courtyard, between the entry to the palace and the Holbein Gate. Despite its name, it was rarely used for dining. Instead, it was a presence chamber, where His Majesty would receive visiting ambassadors or hold other public functions. I wondered how the king felt about the place; seventeen years ago, his father, Charles I, had been executed right in front of it in the street.

The House was a later addition to the palace, built some forty years ago by one of our greatest architects, Inigo Jones. The outside was simple and elegant, seven windows wide, with three central bays and columns on the upper and lower stories. Its face was a mix of colors: pink, honey, and white, created from three different kinds of stone.

As Lord Ashcombe had said, the Banqueting House was unlocked and empty. Inside was one large room, designed as a perfect double cube, 110 feet long, fifty-five feet wide and high. Along both sides of the hall, pillars rose from the floor up to the gallery overlooking the main space. When Charles did dine here, the gallery was where the commoners would stand, to watch our king as he ate.

Tom’s voice echoed in the emptiness. “So what are we looking for?”

The letter hadn’t said. “I’m not sure.”

I studied the ceiling. Between the gilded beams were nine magnificent canvases, all by the Flemish painter Sir Peter Paul Rubens. The scenes were a celebration of the life of James I, grandfather to our king.

“Look for marks on the walls,” I said, “or something left behind, out of place. Anything out of the ordinary.”

“Everything we’re doing is out of the ordinary,” Tom grumbled, and I couldn’t really disagree with that.

Nothing jumped out at me on the ground floor. Below the hall was an undercroft, but before we delved into the dungeon, I figured we might as well check out the gallery overhead.

We went upstairs. Tom took the left side; I went around to the right. A balustrade ringed the gallery, but other than that, there didn’t appear to be anything up here. I studied the floor below, wondering if I might spot something from a higher perspective. When that offered nothing, I looked up again at the canvases.

Directly overhead was a painting of Hercules, wielding a club, stomping on a woman holding a snake, who was supposed to represent Envy. On the other side, the Greek goddess Minerva plunged a spear into another woman, who represented Ignorance.

I really hoped the paintings weren’t the clue. We’d had enough trouble with one in Paris. And there were nine of them here, hanging a dozen feet over our heads. Lord Ashcombe had said we had a lot of leeway investigating for the king, but I didn’t think anyone would be pleased if we started ripping Rubens off the ceiling.