“I have to ask,” he said. “Why did you use impello at the Trocadero Centre—why not a fireball?

“I didn’t want to kill her,” I said. “And I’m still more confident with impello than I am with anything else.”

“You realize she was just a diversion,” said Nightingale. “Alexander Smith was shot in the chest with a couple of narrow-gauge fireballs.”

“I thought it was gunshots,” I said.

“That’s why he used a narrow-gauge fireball to disguise the wound.”

“Forensic countermeasure,” I said. “This guy is way too fucking clever.”

“He probably walked out the back while you were chasing the Pale Lady out the front.”

I cut a target in half with my next fireball.

“That’s much better,” said Nightingale. “They need to go faster. If the enemy can see them coming, you might as well just carry a gun and shoot them with that instead.”

“Why don’t we just carry guns?” I asked. “I know you’ve got a roomful of them.”

“Well, for one thing,” said Nightingale, “the paperwork has become very tiresome, then there’s care, maintenance, and trying to ensure one doesn’t leave it on the Underground by mistake. Plus a fireball is more versatile and can pack more of a punch than any caliber pistol I’d be happy to carry.”

“Really?” I asked. “More than a .44 magnum?”

“Indubitably,” he said.

“What’s the biggest thing you’ve zapped with a fireball?” I asked.

“That would be a tiger,” said Nightingale.

“Well, don’t tell Greenpeace,” I said. “They’re an endangered species.”

“Not that sort of tiger,” said Nightingale. “A Panzerkampfwagen sechs Ausf E.”

I stared at him. “You knocked out a Tiger tank with a fireball?”

“Actually I knocked out two,” said Nightingale. “I have to admit that the first one took three shots—one to disable the tracks, one through the driver’s eye slot, and one down the commander’s hatch—brewed up rather nicely.”

“And the second Tiger?”

“I didn’t have time to be so clever with that one,” said Nightingale. “Straight frontal shot into the weak spot where the turret meets the hull. Must have caught the ammo store because it brewed up like a firework factory. The turret blew right off.”

“This was at Ettersberg, wasn’t it?”

“This was the final act at Ettersberg,” he said. “We were trying to pull out when this platoon of Tigers just came crawling out of the tree line. We didn’t expect the Germans to have anything but rear-echelon troops, so it caught us on the hop, I can tell you. I was the rear guard, so I had to deal with them.”

“Lucky you,” I said. But my brain was still trying to get around the idea that Nightingale could put a hole in four inches of steel armor when I still sometimes had trouble getting through the paper of the targets.

“Practice and training,” said Nightingale. “Not luck.”