“Not one for A,” Middleton said. “Concert pitch. The A above middle C is 440 cycles per second. Each note has a specific frequency. Sharps and flats, equally. A couple hundred notes would yield eighty-thousand digits. Like a bar code. Eighty-thousand digits would yield all the information you want.”

Faust asked, “How do we work it out?”

“With a calculator,” Middleton said. “On the treble stave the second space up is the A above middle C. That’s 440 cycles. An octave higher is the first overtone, or the second harmonic, 880 cycles. An octave lower is 220 cycles. We can work out the intervals in between. We’ll probably get a bunch of decimal places, which is even better. The more digits, the more information.”

Faust nodded. Nothing in his face. He retrieved the Mozart manuscript from the credenza and butted it together with the smeared page in the glassine envelope. Clamped the stack under his arm and nodded to Nacho. Then he looked at Kaminski and Middleton and suddenly leapt forward, ripping the silenced Glock from her hand.

He said, “I wasn’t entirely honest before. I didn’t hire Vukasin. We were both hired by someone else. For the same purpose. Which isn’t entirely benevolent, I’m afraid. We have ricin, and everything else we need. But we couldn’t stabilize the mixture. Now we can, thanks to your keen insights. For which we thank you. We’ll express our thanks practically—with mercy. Exactly ten minutes from now, when I’m safely away, Nacho will shoot you both in the head. Fast and painless, I promise.”

The gun in Nacho’s hand came up and rested level, steady as a rock. He was back in his chair, solidly between Middleton and the door. Kaminski gasped and caught Middleton’s arm. Faust smiled once, and his blue eyes twinkled, and he let himself out.

Ten minutes. A long time, or a short time, depending on the circumstances. Ten minutes in a line at the post office seems like an eternity. The last 10 minutes of your life seems like a blink of an eye. Nacho didn’t move a muscle. He was like a statue, except that the muzzle of his gun moved to track every millimetric move that Middleton or Kaminski made, and except that about once every 90 seconds he glanced at his watch.

He took his final look at the time and raised his gun a little higher. Head height, not gut height. His finger whitened on the trigger.

Then the door opened.

Jack Perez stepped into the room.

Nacho turned toward him. Said, “What—”

Perez raised his gun and shot Nacho in the face. No silencer. The noise was catastrophic. They left by the fire stairs, in a big hurry.

Ten minutes later they were in an Inner Harbor diner and Perez was saying, “So basically you told him everything?”

Kaminski nodded her head very ruefully and said, “Yes.”

Middleton shook his head very definitively and said, “No.”