Well, we still had the grottoes beneath the Banqueting House to search. I was just about to tell Tom I was going downstairs when he called to me. His voice reverberated in the hall.

“Christopher.”

I went around to his side. He was standing at the far end, staring at the railing atop the balustrade, right at the corner. He pointed.

A letter lay folded on top of the rail. I picked it up and saw what was written on the front.

C. R.

Christopher Rowe. Left for me, where no one else was likely to find it.

The back was sealed, a featureless circle stamped in red wax. Just like the letter I’d found in Blackthorn.

I cracked the seal. Then Tom and I huddled by the window to read the message inside.

CHAPTER 18

TOM STARED AT IT, CONFUSED. “What is this?”

Saints defend these ancient walls,

Saints we hope will save,

Visit them in hallowed halls,

And pray upon his grave.

la ruota dell’italiano

B s m v & h c t c q q t d k d & l x

“Another puzzle,” I said, excited. “But I know this one.”

“The rhyme?”

“The code. I know what it is. I need— We have to go back to Blackthorn.”

“Why?”

“There’s a device,” I said. “A cipher device. Master Benedict has one—had one. We need to find it.”

“Oh,” Tom said, pleased. “We’ll get to take the horses—”

I clapped my hand over his mouth.

Below us, the door to the Banqueting House squeaked open. Then we heard the clop of leather heels on floor.

Quickly, I flattened myself behind the balustrade. Tom got down with me, looking puzzled.

Aren’t we allowed to be here? he mouthed.

We were, but what I was doing was supposed to be a secret. I didn’t want to have to explain our presence. What’s more, Lord Ashcombe had said no one should be in the Banqueting House at this hour. It was an awful coincidence for someone to show up just after we’d gone in.

Unless they were here for a similar reason.

Or here for us.

I peeked through the rails. A man stepped into the hall. He was at the opposite end, near the door, but I could make out his face well enough.

I’d seen him before. He was one of the men held up at the palace gate, when Lord Ashcombe and I had arrived at Whitehall during the lockdown. The taller one, with trimmed beard, gold spectacles, and an irate Scottish companion.

He took a step closer, glancing around the hall. A pistol hung from his belt. He held a letter, but this one wasn’t meant for us. It was already open.

He looked around, suspicious. Then he laid his hand on the grip of his pistol.

“Hello?”

Like his companion yesterday, this man also had a Scottish accent. Tom looked at me, eyes wide. I stayed absolutely still, afraid to breathe.

The man frowned. He tried again.