Pope Julius and his cardinals looked up from their war plans. (His Holiness had moved his desk into the library, saying that my happy countenance relieved his stress, especially during arguments with military advisers.) As I wiped my fingers on a rag, Michelangelo stormed into the apartments, face purple as pomegranate. By the looks of him, he hadn’t fed himself in weeks. Or bathed. “I told you, I’m no painter.”

As Bramante and Michelangelo yelled over each other, assistants tumbled up to the door behind them. I slipped down the scaffolding and sidled up to Michelangelo’s head assistant, Francesco Granacci. “What happened?” I asked.

“The fresco mix was wrong. The plaster’s growing mold. He’s going to have to tear it all down and start back over. Three months’ work, gone.”

“Did he use ash instead of sand?”

Granacci looked alarmed. “We were supposed to use ash?”

“If he didn’t use ash, what did he use?”

“A Florentine mix.”

“What?”

Granacci searched my face. “That’s what everyone told us to use.”

I pushed past the others and sprinted out of the apartments.